Guess that matters what you're looking for.So, iPad 4 is where its at?
iPad 2 is hardly CPU or GPU bottlenecked for the most part. Really the two biggest performance complaints for the HW are RAM (most notably for browsing) and resolution. The expectation is both of those will be taken care. So as long as you aren't looking for some serious performance increases (and the SW that would eventually take advantage of it) ... I think you're good to go.
What I expect you'll get with the processor die shrink is similar battery life, with some small improvements in its already good performance. Coupled with the improved RAM and resolution, that seems like a really good improvement to me. If you have the means, I'd say go for it.
Really the only way I'd say no is if you are a hardcore user that wants major improvements on true multi-tasking via jailbreaking. In that case, I'd wait for a quad core assuming this isn't (which signs point to). Once a quadcore is available and someone writes a tight scheduler ... the thing will FLY.