For stills, the iPad's rear-facing camera is serviceable, though the 10-inch tablet isn't the most convenient form factor for snapping photos. For app purposes, it's fine--I used it to deposit a check to my bank without any problem.
I snapped a test shot to compare the fourth-generation iPad's rear-facing camera with the third-generation iPad and the iPhone 5. While the iPhone 5 still has highest resolution and the best quality (fine background details are less blurry), the fourth-generation iPad easily topped the third-generation model, providing a much crisper image. That's due in part to the better camera itself, but also to the fact that the fourth-generation iPad includes a new generation of image signal processor, which improves image stabilization.
Not to be outdone, the fourth-generation iPad's front-facing camera got an update as well. Like the rest of Apple's FaceTime-capable devices, the fourth-generation iPad now sports a 720p camera for video conferencing.
I didn't think I'd be that impressed by the upgrade to that camera, but if you use FaceTime with any regularity, the difference is night and day. I had my colleague Lex Friedman snap pictures comparing a FaceTime chat on the third-generation iPad's standard definition camera and the fourth-generation's HD camera. The HD camera on the new iPad features far better skin tones and a much sharper, clearer picture overall.
Who's it for?
Let's get this out of the way: If you've never owned an iPad, and you want the real estate that a 9.7-inch screen affords, there's no reason not to pick up the fourth-generation model. It's got all of the benefits of the third-generation iPad, and it's a smoking powerhouse to boot.
So, what if you're upgrading from a previous version of the iPad? For owners of the original iPad or the iPad 2, I think the fourth-generation iPad offers a pretty compelling package. Not only do you get a quite substantial performance increase (and, in the case of the original iPad, the ability to run iOS 6), but you also pick up a Retina display, improvements to Bluetooth and Wi-Fi, and--optionally--LTE. That's an improvement across-the-board.
Of course, if the 9.7-inch screen size of the fourth-generation iPad is a turn-off, the iPad mini is a solid upgrade from either of the first two iPad models as well. While I think size is the primary reason to choose the 7.9-inch mini over the 9.7-inch fourth-generation (or vice versa), the major differentiation right now is that the fourth-generation has a Retina display. When it comes to text, especially, that's a meaningful differentiation between the two.