Used mine with a Dr. Z Maz 18 - pretty good results. It's a good cab, and pretty lightweight with the stock speakers considerin' the build quality and what it can do. I've got my eyes on all kindsa heads recently though, so hmmm....
More like a rear-ported design. The slot is only about 2" high.
I have a clone of the THD cab, and it certainly doesn't act like an open-backed cab. More like a closed-back with a hint of airy open-backed character.
I use mine with a mesa Lonestar classis or Shiva - both are incredible through it. Focused and articulate cab that brings out the best in the head IMO. I played last weekend with it ans the Shiva and it sounded WAAY bigger than the Marshall 4x12 set up next to it