This is an expansion for either Toontrack's EZ Drummer or Superior drummer. It's loaded with toms and cymbals and everything I could ever want or need for composing metal or progressive stuff. It's all pre-processed, so using this for anything other than thrash metal, djent, or Dream Theater stuff is a bit awkward, but its punchy sounds and easy to use interface make it a key component of my studio rig.
Also, though I'm not 100% certain, I believe Deven Townsend used this program to create the drum tracks for his Ziltiod: The Omniscient album.
I picked up DFH shortly after it's release and it completely changed how I worked. In the current market it's really nothing fancy, just a nice set of sounds, but at the time this was my first exposure to a full drum library. The drum sound is definitely very much metal. I tried it with other genres with little success (not surprisingly, just for fun). For me though, it's still exactly what I want when writing. It feels good, is inspiring and fits perfectly with my sound.