So far, I've heard of some nasty problems with Windows versions (such as crashing, some audio sounding choppy, and refusal to recognize the new iPod Nano), but I've had mostly excellent results on both platforms (a tired old PowerBook G4 and a Dell XPS P4 desktop). System requirements have increased from the last version, including a 500MHz Pentium class processor with 256MB of RAM--we recommend more for both platforms--for Windows XP/2000, and a 500MHz G3 processor and 256MB RAM for Mac OS X 10.3.9 or later. Like we said, performance is slightly sluggish, particularly when flipping through Cover Flow albums. Video playback (the most processor-intensive activity) is smooth. While I didn't experience the multiple forum user claims of tinny and choppy audio, system crashes, and "breaking" prior relationships with devices and features such as podcasts, I hope Apple has an update that addresses these issues soon.