In one company we had Preforce storing about 20 TB's of information. In a course of three months we had about 100 MB of that data get corrupted to the point the entire repo locked up. We then tried to delete the data but thanks to the corruption, which was caused by Preforce, we couldn't. We ended up on a call with Preforce and it took them weeks to figure out how to solve this problem.
About a year later I started at Blackberry, who were using Preforce. I updated development code into the main repo and BANG! Preforce corrupted the data, except that it didn't know it did, then Maven took the code and moved it out to development test beds which all crashed, costing Blackberry a couple MILLION DOLLARS!!!!
Unrelated to that, I then took another job at an engineering company. They didn't use any SCM or Version Control System, so I grabbed Preforce to see if they fixed the massive issues. I uploaded a copy of the code to the repo and guess what! BANG corrupted.
Preforce is NOT a safe environment, I've seen it corrupt data, cause damage, cause a loss of money, corrupt repo's, crash and just screw up servers. If it were a one off issue, that would be fine, but I've had many, many big issues with it.