All depends on you and what you do with it. I keep mine in an OEM soft shell case and slip it into a holster when I'm going out. No screen protector cuz I don't care for them. The choice is yours.
I'm personally torn between using it plain (possibly with a screen protector) and using it with the OEM holster. One one hand, the thing is so thin, it's a shame to bulk it up with a case. It looks like the pouch will add at least 50% to the overall thickness. On the other hand, the OEM cases -- both the pouch and the belt holster -- have this cool function of automatically switching the phone in and out of standby. Needing that extra step of pushing the lock/unlock button every time I want to fiddle with the phone seems extra hassle.
