One thing about the retina iPads that might be an issue is the heat.

I generally don't do CPU or GPU intensive stuff (i.e. image processing, resource heavy games), plus I use a KeyFolio cover so don't notice the heat. However, our iPad 3 does a get noticeably warm when charging.

Apparently the issue is slightly more pronounced with the iPad 4.

So, if you decide on a retina iPad, I'd recommend a decent back-cover case.

EDIT: Rather, a decent case with a back-cover