My advice:
C.f. an iPad 2, iPad 3 is all about the screen (unless you see any point to having a 5MP camera in a form-factor that's ergonomically useless for taking photos) and most of the extra "grunt" goes to servicing the screen.
I've "upgraded" from an iPad 1 which had no camera at all and was starting to get a bit sluggish, so that's fine. I think I might have been feeling a bit of buyer's remorse now if I already had an iPad 2.
If you plan to use it for viewing photos taken on a half-decent camera or for reading books/documents, or if you have a large collection of 1080p videos, definitely get the new one: the screen makes a huge difference there.
Otherwise, if you can think of better things to do with $100 and your ego can survive having last year's model (its not like you can tell the difference from more than about 5 feet away) the iPad 2 sounds like a good deal.