This is great new for designers and developers alike, and I'm really excited! With ASP.NET 1.x and ASP.NET 2.0, if you wanted to create pure CSS pages, it really wasn't possible. The ASP.NET controls would render with tables, inline styles and all sorts of other things that would make most web designers wince. And for a while, we've had a beta version of the ASP.NET CSS Control Adapters available.
As I was reading through some of my morning news, I saw a post that the ASP.NET CSS Control Adapters have gone RTM! You can download them, and see samples of them working at http://www.asp.net/cssadapters/
If you're doing any kind of ASP.NET development, and want to make your site more CSS friendly, check them out! They're free!