As you may have read in our feature on the Japanese PS3 launch, there have been some early reports of problems getting PSone and PS2 titles to work.
Well, Sony is aiming to help cover that with a backwards compatibility checker website in Japan, which allows you to hunt down specific titles (right down to whether they're the original release or budget remasterings) and see whether there are any problems.
The site reveals a few general issues that won't have much of an effect on gamers outside Japan - PS2 hard disk titles won't work, for example - and also makes reference where necessary to the PS3's lack of compatibility with certain PS2 peripherals like the multitap.
But there are some more specific problems too, including things like screen freezing in Gran Turismo 4 and Devil May Cry, sound issues in Onimusha, Star Ocean and Tekken 5. However Sony has already addressed a few issues with games like Ace Combat 5 in its 1.10 update, and can be expected to keep tweaking as reports of problems become apparent.