I also just received my n800 last week, and flashed with the latest firmware. I currently have a 2gb in the internal slot, and got a 8gb in the external slot. Both are running just fine.
I have a 4GB card internal and an 8GB SDHC card external. Only issue I had was self induced, I took out the external SDHC card while I was playing music off of it. So as long you don't remove the card while it is being used there shoudn't be any problems.
At this point the earlier belief that these issues are limited to the external slot have been pretty much shattered. Browse the forum, you'll see both slots breaking many sizes and types of card, though larger SDHC seems to be most affected.
I think the developers are only able to solve the problem IF they make the effort (and if it isn't a hardware issue). I think the number of feedback and problems reported here and on bugzilla should signal something to them.