Currently they do not offer a free option any more, and my interests are shifted to Git. My current requirements are very simple:
- functional free starter option, with no-hassle switch to payed services when needed;
- both ssh and https access to repository;
- tracking/wiki option (low priority);
- private hosting - no requirement to open-source your code like on github;
I decided to stay with Assembla for now, but keep an eye on CloudForge in the same time. I like their Publisher option - ability to configure your deployment for Joyent, Amazon WS, Salesforce, Google App Engine, CloudFoundry of custom FTP or SSH option. I had not tried it yet, but from description in sounds useful and time-saving.
Update (next day): I've tried BitBucket this morning, and I think it fits pretty well into all my requirements: free, private, https, wiki/issues tracking, web access, integration with other systems. It allows to get more than one user account to the repository, which also might be useful. I'll stay with BitBucket for now.