AT&T's U-Verse app for Windows Phone 7 is fairly snazzy. It's got a full programming guide with DVR remote controls, and you can also download shows to watch later (no streaming yet, boo).
A 30-minute show averages around 80MB, according to AT&T, and should take around 10 minutes to download over Wi-Fi. Yes, you gotta use Wi-Fi. There's also no real integration superpowers between Windows Phone app and U-Verse on Xbox, sadly. But it's not bad for a version 1 app.