I'm using source offsite on a project I'm running with a couple friends. We're building onto an existing fantasy football application using webservices and instant messaging libraries.
I'm very impressed with the performance of sourceoffsite over the vpn connection. This is something that is virtually unusable over Visual SourceSafe (primarily due to bandwidth requirements). The UI is very similar to SourceSafe and the integration with Visual Studio.NET 2003 is excellent so far.