When the PS4 launched back in November, I wrote a primer on it simply entitled, "PS4: Everything you need to know."
I summarized the game console's strong points while pointing out some glaring omissions that I was less than thrilled with. Some of the same features were missing from the Xbox One, so it was hard to go too ballistic on Sony. And to be fair, the PS4's predecessor, the PS3, took a while to add features and fully mature.
But that was then, and this is six months later. While the PS4 has outsold the Xbox One at the rate of about 4 to 3, Microsoft will be soon offering up a $400 Kinect-less Xbox One that matches the price of the PS4. I don't know if the new lower price will allow the Xbox One to overtake the PS4 in terms of monthly sales (or at least keep pace with it), but I do know that I'm becoming more impatient with the pace of Sony's system updates, which haven't to date added any features that I truly care about.
Better media playback support
The PS4 can play Blu-rays and DVDs but still isn't able to play CDs or MP3s, and it won't read any files from an external storage device (via its two USB ports) except system software patches (you have to put the PS4 in a special "safe mode" to do system updates via a USB thumb drive).
DLNA streaming is still not available, and the PS4 still can't play 3D Blu-ray movies, although the Xbox One can't either.
Note that the older PS3 offers support for CDs, MP3s, 3D Blu-ray playback, and reads files from external storage devices. I'm sure the excellent PS4 hardware can support all those features, too -- Sony just needs to make it happen.
Better peripheral support
Except for the PS Move and some wireless headsets and headphones, most of your PS3 peripherals (controllers, and so forth) aren't compatible with the PS4. The same goes for most older non-Sony branded Bluetooth headsets and headphones.
Sony also hasn't released much in the way of PS4 peripherals (for instance, it has not replaced the older Media/Blu-ray remote control with a new one).
Note: Check out this list of compatible PS4 peripherals.
More AAA game exclusives
We've yet to see any truly compelling PS4 game exclusives. Infamous Second Son is a great-looking game that's fun to play, but it's not a system mover. (Titanfall had more sizzle and helped move some Xbox One units, though that was partially due to the game being bundled with new systems for a limited time.) I'm sure we'll see some promising new games teased at E3 in June, but the sooner Sony can get these games to market, the better.
Better selection of 'free' PS4 games as part of PlayStation Plus
So far, the PS3 and Vita are getting all the good "free" PlayStation Plus titles (you pay $50 for a yearly PlayStation Plus membership, which get you some free games, discounts on certain titles, and multiplayer gaming). Granted, there aren't a ton of games available for the PS4 yet, but the PS4 selection is paltry (you can compare the list here to see what games by platform are included with your membership).
Affordable backward compatibility via PlayStation Now
At launch, Sony had hinted at backward compatibility through its upcoming cloud-based streaming game service, PlayStation Now, which will be available on the PS4, PS3, Via, and select Sony Bravia TVs.
There was some hope that you'd be able to use your existing PS3 game discs to unlock cloud-based digital versions. There's some precedence for this in the video world. For instance, for a relatively small fee, Vudu allows you to convert a decent selection of DVDs and Blu-rays into cloud-based digital versions as part of its In-Home Disc to Digital program. (Vudu is owned by Walmart.)
Unfortunately, as it stands now, it appears that PlayStation Now won't give you any sort of credit for already owning a title. It's also unclear whether it's a subscription service like PlayStation Plus or if it will simply be a marketplace for older, non-PS4 titles, and indie games.
More PlayStation Camera games and Skype support
Sony's PlayStation Eye for PS3 didn't sell well, so Sony was very conservative with the launch of the $60 PlayStation Camera accessory for the PS4. Surprise: the Camera has sold a lot better than expected. (As of March 19, Sony had sold around 900,000 PlayStation cameras, and supply was constrained.)
One use for the camera is to broadcast your face while streaming your gameplay via Twitch (for the record, I don't do this). The PS4 also ships with a virtual reality app called the Playroom that requires the Camera to play.
Kids love it, but the Playroom could use some bulking up with more activities. Also, with Microsoft shifting away from the Kinect, this is an opportunity for Sony to one-up Microsoft on camera-based, "moti0n" gaming.
A far as Skype goes, well, it's owned by Microsoft, which seems to be a bit of an impediment. But the Sony-owned Crackle app is available on the Xbox platform, so who knows -- maybe they can strike a deal.
The list goes on...
I'll end my list of wished-for improvements there for now, but that doesn't mean you can't add your own gripes and suggestions in the Comments section below.