Theres a lot of new cool stuff in visual studio 2005 that makes programming better. But cool stuff was aplenty in .NET since it started.
Debug.WriteLine...doesn't seem very exciting does it? It writes some text to the default trace listener for debugging. Woo. But actually, this is very cool. Just spend a little time looking into TraceSwitches, which allow you to define settings in the application config file to determine if stuff is logged (and to what detail), and combine that with a variety of built in trace listeners that can output the debugging information wherever you want it (text file, email, event log) - all controled through the config file, and you've gotta admit its very impressive.
Well I think so ;)