I've been carrying unchambered and unholstered in the AIWB position for quite some time with my G20, and before that, occasionally with my P220. This is as a back up to a chambered OC'd or pocket carried gun.
Being as squeamish as I am about liking my junk, I don't want to carry in the AIWB position with a hot chamber. But if I wanted to carry chambered, I'd probably get one of these
http://www.warriortalknews.com/2010/05/the-zack-concealment-holster.html
I like carrying this way because of comfort, the lack of need to buy larger pants (I barely can fit into 32's and have no trouble stuffing my Glock down my pants with no holster) and the exceptionally good level of concealment it provides. I've had many IWB holsters, and after all of them, tend to prefer this minimalist approach. It isn't for everyone, in fact probably isn't for most people. Just mentioning it for reference.
In terms of any other kind of IWB carry, any holster will work. But the real trick is that you want stability, and adjustability. Durability is nice too. Plus it's nice if the holster keeps rust prone steel away from sweat. On these criteria, the hybrid holster system is wonderful, and justly enjoying explosive popularity. If you're interested in a hybrid holster, the best deal I know of is these
http://hhholsters.highwire.com/product/the-ranger Pretty much the same as all the rest, but cheaper than most, made with 100% US materials, and as durable as any on the market. But there are many others on the market, probably also as good of a deal. I just mention that model because I know the maker from SKS boards, he's very reputable, and offers a lower price than you'll typically see from others such as cross breed.