As I mentioned in my T-Mobile HTC HD2 first impressions article, T-Mobile includes DoubleTwist (both for Windows and Mac) on the 16GB microSD card in the package so you can easily get media content synced to your new device. I just read over on jkOnTheRun that a new version of DoubleTwist for the Mac integrates with the Android Market so you get an even better experience with a Google Android device. With DoubleTwist you now can get an experience similar to iTunes, but there are limitations.
The new DoubleTwist app lets you browse the Android Market, but you cannot download or install apps through DoubleTwist. Still, browsing the Market on your device can be a bit daunting, especially now that we have over 10,000 applications there. You will also find a podcast search engine and playback capability in this new Mac client. I wonder if they will work to integrate BlackBerry App World, Nokia's Ovi Store, and Windows Marketplace for Mobile in future updates too.