Come to think of it, they use BitKeeper's "try it before paying us" model as well. I suppose that's because like BitKeeper and unlike ClearCase, somebody who gave it a serious workout before paying money would still be inclined to pay them.

"I don't care how spiffy the GUI is, it can't eat my code" seems like it should be the first concern in Source Control, but it apparently only is for some of them.

But yeah, Perforce seems to be one.