It works fine for me in Windows and OS X 10.3. I have imported the first 40GB of my library (about 7500 tracks or so) and it works really well. I like how it can export the playlists and the library as XML for later use with other DB apps (for me, it will be ASP.NET/SQL Server). I get about 1-3% CPU utilization during playback, and it takes about 25MB of RAM (about the norm for WMP, Explorer, Mozilla, etc) but feels much lighter. The utilization is lower than WMP, Winamp, Sonique, and other MP3 players I have used, but with a lot more features. I like it a lot, and really dig the smartlists and rating option on the iPod and in iTunes.