I spent some time as a cadet at Hurlburt Field in Florida, where 130s assigned to Air Force Special Operations Command are (were?) based. I also have a few classmates from VMI who are Navs on them (or whatever the USAF calls Navs now).
I know that, in the USAF, the 130 is used as an airlift platform obviously, both in conventional and special operations (Combat Talon/Shadow) roles (one special operations mission is the dropping of the BLU-82 daisy cutter bomb). Also, the AC-130 Spectre and Spooky platforms are used as gunships, and those things are bad ass (excuse the French). I got to fly on a live fire training mission on a Spectre gunship as part of my AFROTC Operations Air Force training, and it was sweet. It has a 105 mm cannon in the side of it that means the aircraft can act as, essentially, an airborne artillery support platform. The AC-130s can be called in for air support and rain down some serious fire. In addition to the 105, there are also 2 20mm guns and 1 40mm gun. I think the armament has changed a bit, but I flew on the Spectre back in 1998.
That exhausts the extent of my knowledge on the 130 for the USAF. I flew on the conventional and special ops version. They are slow and noisy, but I suppose there is a certain charm to them.