So far, I’m impressed.
It really says a lot, actually. It takes a lot to impress me. Sure there are plenty of things out there that are cool, but they’re not necessarily impressive. Basecamp is impressive.
One of the niftiest features, is that it generates both an RSS feed (which is great for an RSS-junkie like me), and an iCal file (compatible with Apple’s iCal as well as Mozilla Calendar). This makes it easy to keep up with my client’s comments as well as my upcoming milestones (deadlines).
I’d suggest it to just about anyone who has a need for (or could benefit from) a project management system. There’s even a free trial. Have a look.