Retina Display: Perfect
Retina HD Display: Perfecter
I love high dpi and I think I would notice the difference, but honestly I have no idea why they are doing this. It is going to have a pretty serious performance hit for no real upside. If they include an ultra fast A8X processor, I can kind of see this making sense, but... meh.
IPad 3 is fine for me resolution wise I'm not sure my old eyes could see the difference. It is performance that I worry about so if this can't be done without a performance regression then maybe it isn't worth it. I say maybe because the screen is a minor issue for me.
As to A8X Apple needs such an updated processor even without Retina HD. ThE one thing that bothers me about iPad is,the,general performance of the device. Also people should realize that it isn't just GPU cores that will or could make the A8X faster, you also have the memory bus which could be vastly improved to deliver better performance.