Well - I wouldn't go that far :-) But they have a great API (and a Rubygem to boot) that makes it simple to sync whatever data you want with them.

You can also setup tags. I have a "might pay" tag based on: 1) signs in often, 2) hasn't paid yet, 3) has added 5 or more tasks and features. These are people I like to keep an eye on and get to know :-)

Another huge vote for Intercom. I use them every day to get to know our customers at http://beanstalkapp.com and the product has saved me a TON of time and made my work much more easy to gain insights from.

It looks interesting but, as someone said here on HN, I'd like to know how much it will costs after beta..