I've been using Mozdev for almost eight years, ever since it started hosting Forumzilla, my project to build a Mozilla-based web forum reader (which eventually became a Thunderbird extension and then Thunderbird's built-in feed reading feature).
Mozdev plays the critical role in the Mozilla community of hosting Mozilla-related projects that aren't considered core enough to the Mozilla mission to host on official community infrastructure. It's a great adjunct to AMO, which distributes many of the projects that Mozdev hosts.
Over the years, I've been happy to host a number of such projects there, including the aforementioned Forumzilla plus Bugxula (defunct), Tinderstatus, and revision control/bug tracking for the Labs project Personas.
Although there have always been alternatives, they have been unpalatable: SourceForge has a cumbersome and unfamiliar interface, and hosting on my own server would have meant doing all my own systems administration. I use Mozdev because I want to focus on my projects, not on the infrastructure for developing them.
Over the last couple of years, Google Code has become an option. Although it provides much less functionality than Mozdev (and limits how many projects you can create), it does have a simpler interface and a more modern revision control system.
The folks who run Mozdev (which includes me) want simplicity and modern services (without sacrificing power) for Mozdev too, and we've identified three priorities in that regard: adding Mercurial for revision control, implementing WYSIWYG content editing, and automating project creation and management.
So I'm thrilled to read Mozdev developer Doug Warner's announcement today, via a post to the project owners mailing list, that he has landed Mercurial support. Now you can get all the goodness of Hg hosted on your behalf for any of your Mozilla-related projects.
Eight years later, I think Mozdev remains the best place to host my projects, and it's just getting better. I can't wait to see what's next (and I have some ideas about what simple WYSIWYG editing could look like, about which more soon).