Here are some of my personal favorites:
- A Visual Studio-integrated designer, that can generate a model from a database, tweak it, and do validation. Now I rarely reach for the command-line tool anymore.
- Project system integration. Everything is neatly laid out in my project window, building "just works" - very nice. More time working on my projects, less time managing them.
- Abstract types and complex types. New "kinds of things" in models that allow me to speak on my own terms more and more.
Of course, those of us working on Microsoft Codename "Astoria" follow the Entity Framework closely because working off of entity models is our bread & butter, so to speak.