We use StarTeam here currently. It runs on both Windows and Linux (contrary to what Mr. Anderson says.) There's a Java-based GUI front-end for Linux that I use daily. It works, but it's a little slow; that might be due to the fact that I'm in Chicago and the server's in Omaha, NE.

There's also an Ant integration task for StarTeam, and it can be used in stand-alone command-line mode, too, if you're hardcore (or for use in daily deployment scripts.) We're currently using the command-line mode, because I had already completed writing our daily deployment script when I found out that it has Ant integration.

One big thing that I've found it has over CVS is that it's not just source code control, but it tracks Change Requests built-in. So when you check code in, you link it to a particular CR. If you want to back out just that CR's changes, you can find all the source files that CR is linked to, and roll them back, leaving all other changes made during the same time period. NOTE: This feature requires developer discipline, which I'm sure you're aware is less frequent than it should be.