I watch streaming movies on my laptop using my Tilt as the modem, but I don't think there's a way to get it to work on a Windows Mobile device directly as you have to install a small activex app on your actual PC (it intregrates into windows media player) and then you watch streaming movies that way.
PS there is a way to download movies from your PC, remove the DRM from them, and then convert them to play on your Tilt. I won't go into that here, but if you google you will find info on how to do that.