Pros
Perforce is still a good place to work at. I enjoy the technology, my co-workers, my commute, the work I do, so I can't complain. Perforce, when privately owned, was a wonderful place to work, but even now it is still a good place. 401k matching, bonuses, massages, bagels, juices/soft drinks, fresh fruit are still offered. Company is still growing and hiring. Change is hard for some people, but it's an inevitable part of life and everyone should take stock of their own situation. If you don't like your current situation you can always go elsewhere.
Cons
The current company is different than the old Perforce, and yes the mood can sometimes be a bit down when people leave to pursue other opportunities. And there is some uncertainty as other companies are acquired.