For the most part, I loved my 3. I still remember the first time I saw that retina screen, I was amazed.
I did not always enjoy having a heater in my lap, and the occasional lags and crashes were annoying. I don't use my iPad for gaming, but more business-related uses. Annotating PDFs was torture on the 3. I finally found an app where I could at least get it done without nearly throwing my iPad at the wall, but that doesn't mean I still didn't think about it occasionally.
I never complained about the weight/size of the 3, but I did notice a difference from the 2. Overall, I probably didn't really need to upgrade - I just wanted to, and had the means to do so, so I did it.
Holding the Air after the 3 is like holding my petite 2 year old niece after trying to pick up my long and lean 8 year old - it is an amazing, very noticeable difference. There is no heat from the Air, doing the same activities I was doing on the 3. It is snappier, and overall smoother.
Even if I wanted to go back, I couldn't, as the iPad shuffle has already taken place. Our son, who inherited my iPad 2 16 gb when he decided to keep that and have me sell his previously-inherited 4th gen 64gb iPod touch to pay for my 3, decided to take our deal of an early Christmas present of my 64gb 3 since he was always running out of room on the 16gb 2. The 2 is going to MIL as an early Christmas present. So I guess I'm "stuck" with the Air.
FWIW, my son LOVES the 3. Or so he says. He mainly watches videos and plays Minecraft, and hasn't noticed any issues. He says it's faster than the 2 (of course, he could be saying that just so he doesn't lose the extra 48gb of space we gave him!). Of course, he did just put Infinity Blade 1 and 2 back on it now that he has room again, so we'll see how those do!
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My big issues with ipad 3 were horrible battery life and it took forever to charge.
How quickly I forget. Battery life and charging time are TERRIBLE. I now charge the 3 with the 12W charger that came with the Air, and use the 10W from the 3 to charge my Air.