I picked up a Nexus 7 immediately and haven't experienced anything of the sort described. I haven't heard any complaints from the half dozen folks I know who own them either.
Same here. My original one had the screen lift issue, so I sent it back and got a replacement, but I haven't noticed a bit of slowness, deterioration, or any other hardware/software issues out of it. I've used it almost daily since the day it was released.