I keep coming back to SVN. Doesn't do everything you want, but it is solid, and I find if it is set up well, other people really get to like it.
We use TortoiseSVN (if you are using Windows) because it really makes SVN easy. I keep looking for anything close to TortoiseSVN on other platforms.
With SVN, you can easily put the whole design project under SVN, but you can easily check out just the part of the project you want - such as the PCB design folders. I have the SVN respositories on a WebDAV web server, so anyone on the VPN network can browse all the projects and files with a web browser. If someone just wants the latest Gerbers for example, they can just get them straight from a browser. You can also capture an address of a folder you need to access, and paste it into Tortoise SVN to export it or check it out. We don't have any project folder on the servers at all.
Every time you commit files, you are asked for comments, and if the whole design project is in the same SVN, it is easy going back to any point of time and getting all the latest files at that instant. Every user has their own SVN login, so it is easy to identify who makes the change.
The way SVN repositories work make them very easy to back up, and SVN does a great job at minimizing storage needs. I have used it when there are hundreds of repositories with tens of thousands of files in each repository - some in the gigabyte size - and I have never had any significant problems. Eliminating all the zip copies of a project is a huge help.