The new client doesn't offer any ground breaking new features. Like SpiralFrog did, it gives you access to music from the major labels that's free, but contains Microsoft DRM. You must be connected to the internet and using a Windows computer to play them.
Although Qtrax has claimed since last year that a Mac version, and even iPod support were on the way, they aren't making any promises about when either will be ready.
There's also no word on when Qtrax will be available outside the US, although that's slated for Qtrax version 1.1.