I'm not a big Basecamp fan - I'm forced to use it for work where we have 40+ projects running on it and sometimes for larger clients when they have their own Basecamp setup.

Maybe we don't use it to its fullest but all it ends up doing is archiving conversation threads and being a file repository. Just looking now there are 3 month late todo items that I don't think will ever get closed. After a while every project seems to drift off of it and end up using a combination of email + bug tracking.