First I've heard of these, let me know if I'm way behind the learning curve here...  I will definitely be ordering a set though, they look niiiicee!  Is there anything I should be aware of carrying IWB magazines in a pouch like this, opposed to their original magazine holsters?  (Also hoping this is the right forum for this thread...)

http://www.comp-tac.com/product_info.php?products_id=135

I have no affiliation with Comp-Tac...  But I do own their products and they make good stuff!

I have a C-Tac holster and like it a lot.  I will be ordering one of there standard magazine holster.  As for your question, I would think it would be similar to an IWB holster.  Due to my body shape/size I don't want anything else inside the belt beside a pistol.

I've got a couple of their standard magazine holsters, and while they are excellently manufactured, I am not too fond of them because I have a hard time hiding them beneath my shirt.  They stick out pretty bad.  But I'm 5'9'' @ 150lbs. so it's hard for me to carry anything.