So I scored a copy of FXpansion's BFD for Christmas, from Santa Claus of all people. While there are some issues, which I'll touch upon briefly, the basic idea of the plug is to completely obviate that most annoying of creatures, the drummer. And it does this in pretty convincing fashion. After spending some time learning the ropes, I threw it in a song and was immediately impressed with the fact that I couldn't tell it wasn't a real drummer. I imagine a good drummer could tell, but those are few and far between, so there's not much danger there.
Of course, the ability to actually program drums that sound like drums is a plus, so some experience with the real thing is necessary; it's not a Magic Box or anything. There are some included MIDI grooves in various modern styles, and I suppose they're usable, but not my cup of tea. The plug (which is essentially a sample playback engine) makes it relatively easy to get a kit that _sounds_ like a set of drums; the actual programming needs to be _played_ like drums in order to complete the illusion.
The included kits are pretty good. Some modern kits and some vintage ones, for a range of sounds. I like the Slingerland set the most, except the foot is just about the biggest piece of flab you're gonna find. So I swap that out with one of the other feet, and I'm in business. You get control over the 3 sets of ambient mics (room, overhead, PZM) and the close-mic'd set. Adjusting these parameters to taste gets you your sound, whatever is appropriate to the song.
CPU-wise, it isn't much of a hit. It is hard on RAM and the drive, but I've got tons of both, so not much problem there. The only real problem I have is getting a good balance between the foot and the snare. Just using the stereo version of the plug, it's difficult to find a place where you can hear both. You have to use a lot of room or overhead to really hear the snare, and when you run the plug through a compressor, it brings out the room more, so it's a bit of work to not end up with "When The Levee Breaks" kind of shit.
The other problem, and it isn't so much of a problem as a matter of taste, is that normally when the foot gets hit, or the lower toms, the snare will also make quite a bit of noise. There is none of this here; they obviously turned off the snares on the drum kits when making the samples. This one added bit would really set it off, I think.
UPDATE: If I paid more attention, or read the manual or something, I'd know that this isn't the case. Some of the kits have the snare on for every hit, and others have an extra foot 1/2 step below the normal one (that I didn't notice because it was on the bottom key of my controller) that has the sound with the snares active. Thanks to musicjon for pointing out that I'm stupid. Don't make a habit of that!
Anyways, this is a stellar piece of work, and Angus and company should be proud of it. I strongly recommend it if you do any sort of music that requires "real" drums, and you don't want to go through the heaving mess of problems that Captain Caveman brings to the table. It's $329, and worth every penny.