hazmat: If your cell phone has Bluetooth, the Rendezvous technology synchronizes your address book to it. Rendezvous is broken in Jaguar Dev Prev, however, and I don't have a Bluetooth cell phone to test it out with, either
Tom Head: the mail app is significantly faster this time around, and has a ton of small little improvements that make it better, but overall, yes, expect to be very excited with the final product... mail.app has evolved!
Address Book is EXTREMELY fast and works very well. It is very well thought-out and works with iChat in an incredibly seamless way
the pictures feature really is nice... I never thought I'd use it but iChat lets you scale and move the pictures around before you commit to a final image, and the image gets updated in the address book (just tell iChat to use an address card for one of your buddies, and all sorts of amazing things happen: Mail.app tells you when that buddy is online, lets you send an IM FROM Mail, and iChat's photo prefs for that buddy get saved into the address book. In addition, there is an "email" button in the iChat window--click it and Mail opens up with the correct address filled in. The integration is amazing!
It's a great time to be a mac user
OS X 10.1 brought much-needed speed enhancements. Jaguar brings Quartz Extreme, much better multithreading, and a TON (and I mean a TON) of usability enhancements. I find the "screen flash instead of alert sounds" to be a really nice feature--basically, any time you'd hear an alert sound normally, you can elect to have the screen whiteout for about a quarter of a second. I like it because a) it looks better than the manubar flash that OS 9 had, and b) I hate having an alert sound when I'm listening to music (or in the middle of the night, when I have headphones on), so for me, this is a very attractive alternative. It's very sleek, not "cartoony" at all.
Another thing I've found is that the Aqua globe, aka the new Beachball of Death (which appears much less frequently) will appear if you move the mouse over an inactive that has something busy in it (example: if I move the mouse over Mail when it is in the background, and it's checking mail, the blue globe comes up to let me know that Mail is doing something). When you move the mouse off the window, it resumes the normal mouse cursor look. BTW, you can click to the "busy" window, and it will work just fine. The Globe is just there to let you know that it IS doing something. I personally think that's a GREAT step forward in terms of really seeing what's going on in your system....
I LOVE JAGUAR!!!!!