PDC - My mind is aglow with whirling, transient nodes of thought careening thru a cosmic vapor of invention.

I have to admit I am overwhelmed! The keynote today was simply amazing. Don, Chris and Scott did a bang up job demoing all the various tech working together.

C# 3.0

LINQ is totally awesome!
Extension methods rock!
Lamdas make alot of the anon delegate stuff easier.

Web

Atlas looks great!
IIS7 is to Web servers what SQL 2005 is to databases. (managed code is finally a 1st class citizen)

Rich Client

All the avalon sample apps are really sowing off the power of the platform. Everyone I've talked to has had nothing but good things to say.