I posted your message to her, and here's what she had to say (over IM):
[Serena] is one of the best.That being said, I've worked with PVCS before and, like Scott, I wasn't all that impressed by it. I'd much rather use CVS or SVN. But I'd also rather use PVCS than MS VSS.
The only real gotcha is that you have to know what your going to do when you first set it up for the upgrade. You can't plan as you go or it will take you more time in the long run and just move over the code to a fresh new project and blow it away. though this doesn't sound like much it is time consuming.