Nintendo had something like this with the GBA.. They said it was fully compatible, but there were some problems with some games.
Boasting about "full backwards compatibility" is good and all, but when you are, make sure it's not just in theory.. If you're saying stuff like "full" and "100%", then I assume you've tried all 16,000 games, and know that they work. This goes for both Sony and Nintendo, and anybody else who says their console is fully backwards compatible.
And if 8,000 of your 16,000 games don't work, then I'd like to see some people fired!
