I've completed the pro Zelda perfect now, but after a while playing pro Mario I can pretty much definitely say it's out of sync with the music - the arrows are slightly ahead of the music so you need to play each note very slightly before you hear it. I can still do pretty well and I'm confident I could perfect it, but it does make it a lot harder when you have to play out of sync with what you're hearing.
Still progressing on the Pro levels. I've managed Zelda perfect except for adding one extra note (100 points off perfect) and I'm not stopping until I get it!
So far I've got 10 perfects on Amateur, 1 perfect, 2 golds and 6 bronzes on Pro. I think this is an excellent game and has just the right level of challenge. I've not experienced the lag a lot of others have, and I don't think that timing is off at all, except for a couple of very small sections (and it's easy to compensate for it anyway); I guess either some people are experiencing a problem with the way the game runs at their end, or are simply too inaccurate with their key presses and so assume that it is out of sync.