The iPad 3 is shaping up to be a repeat of the iPhone 3G (read: only survives one iOS update before becoming slow enough to impair its usefulness).
I think that comparison is invalid. The biggest problem with iPhone 3G was its lack of RAM when iOS was upgraded, which isn't a problem with the new iPad as it now has 1G of RAM.
I predict next year the new iPad will be released with 1G of RAM and the same Retina display, and people will complain how that isn't a "true" upgrade because the display, LTE and the RAM have not changed, telling everyone how they'll wait for "iPad 5" which will be the "true hardware upgrade". Then the next year people will complain how the new iPad isn't a true upgrade and...well you get the point