iPad 3 pros: retina, 2x RAM, better camera with 1080 video, better graphics (offset by higher res screen though), dictation, LTE (optional)
Cons: heat, battery life, weight (minor), thickness (very minor), charge time.
I bought an iPad 3 and returned it, going back to my iPad 2. It's not that the iPad 2 is better - it isn't. But for a current iPad 2 owner, it was a lot of money for an upgrade that was actually a step back in several respects. If I could have either at the same price, I'd take the 3, but not by that much. The screen is the big deal, and the LTE, if you have it (I don't). The camera, not like I'd ever use a camera on a tablet. Dictation, nice, but I type very fast on the iPad. graphics, no benefit once you consider it has to drive the new screen. RAM, nice, but iPad 2 hardly runs out of ram that often.
Likewise, the big loss was battery life. The other things are annoying, but minor, like the gains on the other side.
So the question was, is it worth a few hundred bucks for the retina display and losing battery life? I said no. My iPad 2 is going very strong. I'll see what the 4 looks like.