I was just wondering if anyone has used the new powerflex 755 drives, and if they have used the safe of module. If so any problems or issues with the drives.

Not yet, but we have a ton of drives 7,70,700 slated to arrive during the summer slow season for install, I'll keep my eyes peeled.

What have you heard or are on the lookout for?

I have not heard one way or another, but I am looking at them for a new project I will be working on, I mainly ask because I installed four new Powerflex DC drives and had some issues with the fermware and other problem as I tried to get them up and running. So I wanted to see if anyone has installed on yet.

No experience with that particular drive. However, the "safe torque off" or "safe off" module is becoming wide spread on all drives. It first appeared in servo drives to solve a lot of lockout headaches. Since you can't draw power (at least enough to turn over the motor, except on a permanent magnet motor) if you don't put power to the gates on the IGBT's (or SCR's or GTO's or what have you), that's the operating principle behind the "safe off" stuff. They appear to be using safety-grade relays and it's pure hardware. Firmware has nothing to do with it.