I carry my Glock 26 IWB at 3:00 - 3:30 without a holster (I usually wear a belt to keep it tight).
If also have an Uncle Mike's Kydex Holster for the Glock whick I wear at 3:00 as well.
I think coming straight up out of the holster without having to swivel the gun allows for quicker target acquisition and you end up pointing the gun at less bystanders. It is also harder for someone to prevent you from drawing as opposed to shoulder holsters and SOB holsters. SOB holsters are uncomfortable as heck when yo have to sit. Just my $.02 worth.