Was given an IWB holster the other day. Kind of a semi-rigid nylon that fits the 21 and 30. About 2 seconds with it in the pants drove me nuts and I put it between my belt and pants. The thought of a loaded weapon inside my pants bothered me. It is also much better feeling and a little closer to my body and doesn't print like an OWB holster. Still have to be concious about it showing from under my garment. Even if the bottom peeks out all of my holsters fully cover the barrel so no one actually "SEES" a gun should that happen.
I carry Condition One. With the 1911 I use a holster that has a strap that fits between the hammer and slide and fully covers my ambi-thumb safeties. For the Glocks I have a holster that has a retention strap and some that don't. The one with retention is when I'm walking about in public and don't want the gun flying out should I be tackled or snatched from me.
The "strapless" is when I'm working.