The Good: The Apple iMac's 27-inch 5K display remains the most color-accurate monitor we've seen thus far in an all-in-one, and performance is much improved. Plus it's got two USB-C\/Thunderbolt connectors which can drive more external displays and faster file data transfers. The Bad: The overall design remains unchanged since 2014 -- including the inconvenient rear-mounted ports and SD slot. The Bottom Line: The already impressive 27-inch 5K iMac gets some welcome spec upgrades for 2017, but rival Windows machines have closed the gap. Apple dusts off its veteran 27-inch iMac all-in-one, updating it just enough to bring it up to 2017 standards for speed and features, as well as to brighten its 5K display and give it the ability to simulate more colors. In practice, that means Apple incorporated 2017 versions of Intel processors and AMD graphics, added support for Bluetooth 4.2, and replaced the old Mini DisplayPort connectors with two Thunderbolt 3-capable USB-C ports. These modest updates were announced at Apple's 2017 WWDC conference, alongside similar spec bumps to the 21.5-inch iMac, the MacBook and MacBook Pro lines, and even a very small CPU bump for the MacBook Air. In fact, except for the Mac Mini, nearly the entire Apple computer lineup has been refreshed for 2017.This model does deliver a significant speed boost over older models, with performance comparable to current Windows competitors. Plus, at least for this fleeting moment, it's the only all-in-one to offer Radeon RX 580-class graphics (in the guise of Apple's custom but seemingly identical Radeon Pro 580 version). The Retina 5K display also remains best-in-class, as well as easier to configure than most Windows 10 systems with their needlessly confusing integrated\/discrete graphics architecture. The fast data transfer rate of the Thunderbolt 3 ports helps for future-proofing, but at the moment there aren't many drives that can take advantage of the spec's 40Gbps bandwidth. There are a few fast, expensive SSD RAID configurations -- the fastest I could find topped out at 22Gbps (2,800MB per second) -- but most current drives are designed for USB 3.1's 10Gbps maximum.However, if you have the 2014 or especially the 2015 5K iMac, none of those changes offer a compelling reason to ditch your current system right this minute unless it's earned an "I brake for Netflix" bumper sticker. And if you've waited this long you might also want to think about waiting a little longer until MacOS 10.13 (High Sierra) ships in the fall to save yourself a time-consuming upgrade. Or, if you need something with more power but that's still an all-in-one, you could wait until the end of the year and try the upcoming iMac Pro, which packs considerably more powerful Intel Xeon processors and AMD Vega graphics into a largely identical (but space gray) body.Still a solid designThe iMac has stood up pretty well over the years and continues that trend. True, it's no longer a system that you can really get excited about as cutting edge, and the static feature set isn't as comparatively impressive as it was when it first shipped. Of course, a lot of that has to do with Apple's no-thank-you stand on newer technologies such as computer touchscreens or wireless charging; that limits the scope of new hardware features it might add. The Retina 5K is still the highest resolution display in an all-in-one, but now it has to compete with larger ones, such as the HP Envy Curved 34-inch, and sufficiently high-resolution-for-most-people 4K models. In the context of current 27-inch all-in-one designs it's still quite functional and I have no complaints about it, with the exception of the SD card slot on the back. (And the fact that you have to wait for the $5,000 iMac Pro for a UHS-II compatible slot.) But it's starting to look a little tired with its wide bezels around the screen. HP's Envy models look more streamlined and the Dell XPS 27 puts USB connectors and the SD Card slot on the side of the display, a more convenient location. Oh -- and the XPS 27 also manages to pack in a kick-ass 10-speaker sound system. Pricing hasn't changed at all for the 27-inch model -- $1,800 (\u00a31,750, AU$2,700) for the entry-level version we tested -- which seems on target for what it offers. The base model is a reasonable configuration for the money; if you want something more powerful, I'd probably suggest a big bump to the Pro 580-based model, with a Core i7 and 16GB memory, at $2,700 (\u00a32,610, AU$4,090). For in-between configurations you most likely won't see significant performance increases that merit spending much more, unless it's to switch completely to SSD from the Fusion drive and\/or increase the amount of memory, which now goes up to 64GB in the more expensive 27-inch iMac but still 32GB in the entry-level model. Ch-ch-ch-changesGiven the small set of updates, I'll focus on the significant "deltas" -- performance and display quality. I did test drive an external 34-inch curved monitor via the new USB-C connector and it worked, but every monitor is different so it's impossible to generalize from the experience.