The Asus PadFone (September 2013) is a promising beast of a phone, with a stylish, sophisticated design, a pixel-dense screen, and gaming performance that puts even dedicated gaming devices to shame.

This new version is a followup to the PadFone Infinity, released just a few months ago. The upgrade retains the design of the older model, but swaps out the Snapdragon 600 for a Snapdragon 800 and adds a microSD slot to the phone's body.

To be sure, the PadFone is still a phone that plugs into a 10.1-inch screen to become what is essentially a full-size tablet. Only now it's faster and gives users an always-appreciated storage expansion option. If you're skeptical about the whole concept, we get it. So were we. It's just one of those things you probably have to try before you can completely understand how useful it can be.

We spent a few hours with the phone-tablet. What follows are our first impressions.

What's different?
Externally, this PadFone duo looks almost entirely the same as the PadFone Infinity combo we saw earlier this year. The devices have the same dimensions and docking design -- in fact, the docking station is unchanged from the previous version, down to the part number. Inside the phone, however, a few important changes await.

Android 4.2.2 Jelly Bean makes its home on this new PadFone, compared with Android 4.1 on the previous model. Behind the scenes, Qualcomm's 2.2GHz Snapdragon 800 quad-core processor replaces the PadFone Infinity's still-impressive 1.7GHz Snapdragon 600 chip.

Josh Miller/CNET

Digital pack rats and collectors of photos, videos, and games will be thrilled to know that Asus has added a microSD card slot that can hold up to 64GB in external storage (to go along with Asus' free two-year gift of 50GB in an online locker).

Let's talk about the phone in PadFone
The heart and soul of the entire operation, the PadFone smartphone is no mere gimmick or proof of concept. It's a sleek, carefully designed piece of high-end machinery that evokes style, sophistication, and raw force.

Much of that impression of strength is owed to the brushed-aluminum alloy unibody design, which comes in black and white, and which Asus boasts is made from aerospace-grade material. The tops are slightly more rounded than the squared-off sides.

Josh Miller/CNET

Though the 5-inch 1080p HD screen takes up a lot of space, the slimmer, taller dimensions (5.6 inches tall by 2.9 inches wide by 0.35 inch deep) make it easier to operate one-handed. It probably goes without saying that the phone's comfort in your hands depends on your hands. One of us found the edges a little steep and sharp, whereas the other complained that the phone felt a bit too wide, even with his large hands.

At 5.1 ounces, it has solidity and weight to spare, a side effect of its aluminum construction. The new microSD card slot sits next to the nano-SIM card slot, which requires a tool (or paper clip) to poke out.

Besides the large, high-resolution LCD display (with in-plane switching, we might add), the PadFone's other specs keep pace with the elite smartphone pack, including HTC's One, Samsung's Galaxy S4, and LG's G2.

Josh Miller/CNET

The Snapdragon 800 processor is really a highlight, and that's something we break down below, so read on for results from a battery of benchmarks and real-world tests.

Like at least a few of today's top smartphone cameras, the PadFone packs a 13-megapixel shooter equipped with autofocus and flash, plus a host of extra camera software features. A 2-megapixel front-facing camera joins the fun, along with a large 2,400mAh battery.

You'll get two storage options, 16GB and 32GB. There's also support for Bluetooth 4.0, an FM tuner, and NFC.

Josh Miller/CNET

Asus' take on Android
Android looks a little different on the PadFone, so if you've never seen the two together, let this be a brief primer.

Asus has touched pretty much every screen, but Android more or less operates as you'd expect. The pull-down notification shade has extra toggles for reading mode and others, along with quick-access settings.

Android on Asus PadFone
Left: Asus adds some extra functionality to its notifications shade. Right: Press and hold the home key to pull up shortcuts. Screenshot by Jessica Dolcourt/CNET

In the app tray, you can also view and sort programs using several filters, say, seeing your most frequent selections or apps that you've downloaded. There are some Asus-made widgets as well, like the one fixed to the home screen by default, which opens up your inbox.

If you expect to see Google Now when you press and hold the home button, you may get a jolt when you see what happens. A toggle pops up instead, which lets you open Google Now, yes, and also shortcuts to voice search, the calculator, browser, calendar, gallery, settings, and more.

Android on Asus PadFone
The PadFone contains lists-within-a-list of device-specific settings, including apps set to switch over to tablet mode when you dock. Screenshot by Jessica Dolcourt/CNET

You may wonder what happens when you take an Android app configured for the PadFone and open it up on the dock. Asus has customizable software for that, too. A checklist for what the company calls dynamic display switching helps govern which apps make the transition from the 5-inch to the 10-inch screen.

All about that docking station
Once plugged into the docking station the PadFone for all intents and purposes becomes a full-on 10.1-inch table,t and quite an ergonomically sound one at that. The brushed-aluminum feel of the phone is lost, replaced with a much softer, rubberized and comfortable one; however, the rear-side undulation -- the result having a 5-inch phone stuck in its back -- is a little off-putting and distracting when holding the tablet.

And while the phone is pretty well locked into place under normal circumstances, a forceful enough jerk will send it flying from the station. A more secure locking mechanism could prove useful if you plan to share the tablet with others. The station's corners aren't as rounded as I'd like and burrowed into my palms.

Josh Miller/CNET

Curiously, while the PadFone and PadFone Station can both be charged independently and the Station's battery will charge the PadFone's battery if it's plugged in, the Station can't be charged by the phone's battery and must have at least some charge -- or be plugged in to power -- in order to function.

Not funny
The Snapdragon 800 is no joke. At least, judging from its performance when running 3DMark. It scored a bit higher than the previous champion, the Nvidia Shield, but things really get interesting when looking at the details of each test.

3DMark (unlimited)
(Longer bars indicate better performance)
Asus PadFone (September 2013)
Nvidia Shield

Graphics Test 1 (GPU)
(Longer bars indicate better performance)
Asus PadFone (September 2013)

Graphics Test 2 (GPU)
(Longer bars indicate better performance)
Asus PadFone (September 2013)
Nvidia Shield

Physics Test (CPU)
(Longer bars indicate better performance)
Asus PadFone (September 2013)
Nvidia Shield

3DMark's Graphics Test 1 throws a huge number of raw polygons -- with minimal effects added -- at the processors. Housing a 1.9GHz Tegra 4, the Shield easily takes this test, rendering the polygons at rate of 108 frames per second, compared with the PadFone's 91fps.

Graphics Test 2 on the other hand has each device render fewer polygons, but to keep things interesting, includes many more post-precessing effects like particles, blurring, and high dynamic range.

The PadFone comes out on top in this test, besting the Shield's 52.7fps with its own 67.2fps. In CPU computational speed, the devices were neck and neck, achieving about 52fps each.

Josh Miller/CNET

So, what does this mean. Well, it actually doesn't mean much. However, the results definitely do indicate two things: one, the processors at the aforementioned clock speeds are pretty much equal in performance, and two, the Tegra 4 appears be better at pushing a high number of polygons with minimal effects, while the Snapdragon 800 brushes its shoulder when confronted with processing effects.

Availability and outlook
The Asus PadFone is an already impressive and promising device. Right now, it's only available in European and Asian markets with no planned US release. Which is a surprising shame given its high-quality design and powerful innards.

The concept of turning your phone into a 10.1-inch tablet is one of those features you don't necessarily think to pine for, but once experienced, it's like, "Yes, of course I want that!" And I can't believe it's taken so long for manufacturers to get this close to right.

If nothing else, the PadFone represents not only Qualcomm's ability to compete with Nvidia on equal footing, but also Asus' willingness to continue to try new and sometimes goofy, but usually interesting concepts that more often than not appear to pay off. We haven't spent enough time with the PadFone to give a buying recommendation, but Asus seems to have gotten the hardware right. If it's ever released in the US, the real questions will be, "When?" and, "How much?" Hopefully, Asus will have pleasing answers to both questions soon.