I've always hosted my open source applications at SourceForge. When I first started developing open source applications, it was the de facto standard. When it came time to find a host for my new iTunesExport-Scala application I decided to check out the landscape. The primary sites I see these days are Google Code and GitHub. Since I have not yet embraced Git I decided to give Google Code a try.
What do I think? I like it. All the Google applications seem to have a common theme: they are simple to use and cover the core 80% well. In fact, their approach is a lot like Apple's approach. Google is just an uglier Apple. :)
Setting up Subversion, doing releases, and editing the home page were all much easier than on SourceForge (even after their redesign). The site is fast, and integrates with Google Analytics so I can track traffic in the same tool I use for my primary website.
The bottom line: It just works.