The only button that's dirrerent S3 vs S2 is the aspect button? I read a thread sonewhere about the Tivo button being different. It's how the S3 figures out which remote you are using (old vs new). If you use the wrong one, one of the buttons acts as "guide" instead of switching tuners (forget which button and I'm not at it right now). So there's apparantly at least 2 buttons different.
Jerry: I'm making a MX850 file but from pristene "programmed" hex codes instead of learning. Once I get the protocol, device id, etc. I can get all button possibilities, then figure out which codes do the "new" stuff. I've had issues with learned codes in le, the past and when reverse engineered they often show a lot of garbage in them. So when possible, I program them from hex/scratch.
Edit, it's the Live TV button that hiccups if you use the wrong remote: