It's pretty cool -- basically a Flash-based Web2.0 genealogy app. The site has been a bit slow from time to time, and it doesn't seem to like the version of Flash on my Fedora Core 6 laptop, but works fine from the Windows and Mac machines I've tried.
Apparently other people in my family think it's neat too -- I added about 24 people to my family tree, and by end of last night it was up to 80 people!
I'm curious how they're going to handle linking trees together, and collisions between trees (ie, someone vaguely related to me sets up an independent tree and eventually we add the same person).
There are some privacy concerns too -- they give the opportunity to provide a lot of information about yourself, and explain that the information is only available to people in your tree. But what happens if/when they start linking disparate trees together, and your tree is linked to the tree of an 18th cousin who doesn't know you from a hole in the ground.
Still, interesting stuff. The UI is excellent, and when the back-end isn't bogged down the whole thing Just Works(tm).