I can't tell you anything about the other Manufacturers' holsters mentioned here, but I can tell you about the Kramer.
I have one for a Kahr PM9 that I carry daily. I've had it for about 4 months now and have a few observations.
It was too tight from the factory. However, they have instructions on the website on how to loosen it up some, and it definitely loosened up to what I wanted.
It's definitely not as fast as having no holster as williamlayton observed, but you have to qualify that statement with mine. If you have your hand on the gun, the draw is the same with or without the Kramer. If you don't have your hand on the gun, it's slower with the Kramer, no doubt about it.
If you carry without a pocket holster, I wouldn't put anything else in the pocket...but that's just me worrying about something tripping the trigger. The Kahr doesn't have a safety as it's DAO and it's something I think about. With the holster I don't have to think about it as the trigger is completely covered.
Just food for thought,
Ka6otm