I wrote up my initial impressions on Facebook now that it went live here:
Added notes for the code monkey crowd:
This is easily the most cross-referenced database I've ever seen. Everything in a profile can be clicked on and matched with other people in your network or friends list. It's not rocket science to do, but you don't see it very often. Sites like IMDb and RCDB do this, but you'd think it would be a more common practice.
The AJAX stuff is all over the place, mostly in the form of auto-completes. Typing in your college name, for example, is infinitely easier than having to do some awful drill down of drop-downs.
The photo uploading tool is really cool. Remdinds me a lot of Kodak Gallery, only better. It's also Java-based, so it just worked right away on my Mac in Firefox. The tagging mechanism is cool too, particularly how it (again) cross-references to other profiles.
Will it catch on with "grown ups?" Hard to say, but I guess time will tell.