Jeez - this puppy is loud! I'm running a GBE 600 head into it (425W @ 4 ohms) and I CAN'T make it fart! It rattles everthing in the house, but it's sweet as hell - no internal rattles, enormous punch, scary low-end - just awesome.
I bought the head (see my review) because I loved the cab, having heard it a while back just in passing at a music store.
The only downside might be the weight - but it's kinda like airplanes...you can carry a pile o' bombs and go slow, or go really fast and carry bullets. This one carries a good bomb load and just enough bullets.
You want a bass cab that can deliver some oomph? This one is pretty damn good at 90 lbs and an SPL of 103, and louder than the Ampeg "fridge" (8 x 10's at ~150 lbs... which is way too heavy). I guarantee you that this cab is louder and cleaner than two 1x15" EV's (used to have them), and the low end response is amazing.
This G-B cab is absolutely flawless for my purposes, but if you're a low-volume jazz player, or into quiet gigs, this is probably more than you want to carry around.