I've been using ACT by Sage for quite a while but their proprietary grip on my contact notes is ridiculous and unacceptable.
It seems like now that XF offers the ability for custom fields, we could be pretty close, especially by adding a Calendar plugin for task reminders, etc.
I would buy a separate license and restrict access just to my staff for handling contacts, contact notes, schedule followups, attach files, etc.
Seems like the XF core (now with custom fields, and a nice array of 3rd party add-ons and plugins) could get this job done, so I wouldn't have to park my company-sensitive data on somebody ELSE's cloud server such as 37Signals or some such, but could run it on my own server.
I'd sure appreciate some serious suggestions about this!