Well, I just got an invite to GMail. I am a special boy. They don't allow underscores in their usernames, though, so I had to settle for
hot.pastrami@gmail.com.
First impressions... clean interface, snappy response time. I like the reply box being at the bottom of a received message, and I like the conversation view. It seems a bit short on customization options, but they are in Beta, so maybe there are more on the way. And I don't see any way to import mail or consolidate mailboxes as Yahoo Plus allows, so GMail won't be my primary contact address, barring any upcoming changes in that direction.
So overall, it has lots of nifty new ideas, and a lot of potential. Here's hoping... the guys at Google are clever sons of bitches.