It is no surprise that Microsoft had and still has issues with BC. It was a feature they promised and ultimately didn’t quite deliver on. It is the reason I still own an original X-Box, something I wish I could have replaced with my 360.
Sony did it seamlessly with the PS2 playing PS1 games and I fully expected the same thing out of the PS3, but reports are surfacing that that is not the case. Apparently 196 PS2 titles are having issues ranging from a lack of sound to full on freezing.
Sony did state that we should expect less than 100% BC with PS2 titles, but did promise an update in the future to fix the issues. No word on when we can expect that update. I am working to track down a list of titles having problems for you.