I happened to go to one of the class from a mentoring company. It was presented by Bob Beauchemin-Niels Berglund-Dan Sullivan. Boy! they were great!
I was just in time for the ADO.Net presentation that Bob made. He talked about top 3 features that he liked in ADO.Net
1. Provider Factory - He talked at great lengths about how easy it was to use provider factory to write generic code
2. Meta Data/GetSchema - The easy way to get meta data Schema. More information in his article in MSDN - (link)
3. Tracing - Yes, we shipped a way for you to get trace output from System.Data internal code. Now this is the feature that
was not that well documented in Beta docs, but this article (written by bob, grin) does a very good job explaining the internals and how to get it working.

It was great to see these guys present. They were awesome and great! (Oh, did I already say that :))