To answer the OPs question:
I have seen many of these holsters you mention. I do not personally use them. My OC holster is a level 2 retention holster for the same reasons already mentioned by yourself, James, and FirearmsInstructor.
Basically, regardless of retention, if you are looking at a truly BAD person, they have likely already figured out how to defeat your retention mechanisms ( as already mentioned as well by Wolf) I'm just making it more difficult for the opportunist to make a move. Also, it makes me feel better knowing that even sitting, standing, running, whatever, I don't have to worry about the weapon coming out. Some retention holsters do sacrifice speed on draw so you would have to determine if you want to worry about that or not as well. Many with push button type releases do not sacrifice that speed, while others are more secure but do require a separate action prior to draw.
That being said, I have OCed my CC holster, which is only friction based. I made sure to keep myself a bit more situationally aware than even when I OC my serpa, and wouldn't have problems doing it again, but for my regular OC I will keep the Level 2 retention.
Just weigh the pros and cons, I'm certain you'll find a holster that fits your exact needs/wants!
