I've just started playing with it -- so far pretty nifty alternative.

- integration with Facebook/LinkedIn/Twitter/Gmail

- sends you a daily email reminder of birthdays, info on your meetings that day, contacts you should hit up, people who got new jobs (from linkedin)

- don't think dedupe caught all my duplicates, but it worked ok.

- no exchange support :(

- design is pretty ugly, but the features are really nice.