Looks really nice, and I can't wait to get an invite - but apparently, at the moment there are only 200 users with no invite system whatsoever. :-( Two of the nicer looking screenshots:
I'm really looking forward to trying out this automatic parsing of sentences in the above screenshot - if that is what it does. From what I can tell, you would type in " Dinner with Michael at 7pm tomorrow" and Google would give you an appointment titled "Dinner with Michael" at 7pm on the next day. (Just thought that needed some explanation :P) This would be a really great feature to see implemented into any other calendar app, but I still like the idea of having calendar integrated into Gmail. Synchronization with PDAs and smartphones would be cool too (or even iPods?). At the moment, I'm using Mozilla Sunbird.