I have it.
It is really good for realistic (acoustic) drums. No synth or electronic drums.
The focus is on NN-XT based drum kits though there are a number of Redrum kits as well.
The refill primarily consists of quite a few combinator based drum kits. Each combinator includes an NN-XT for each instrument of the kit (one for kicks, one for snares, etc.) There are also channels for room, overhead, and snare bottom mikes to add more ambience for a more realistic sound. The combinators also include EQ and compression on each drum and are submixed down to a stereo
The only percussion is claps, and tamborines.
The refill also includes some canned midi drum beats in a variety of styles that you can plug into Reason's sequencer.
The refill works very well with jazz, r&b, and rock, but it will take some tweaking or something to adapt it to hip hop.
If you have Reason, then this would be a slightly more flexible solution than BFD, though BFD might outshine it in a couple of areas. I think it's at least worth its cost, especially if you are into other genres of music besides hip hop. If you are hip hop only, this might not be a good fit.
Hope this helps.
cycloptic