Wow, not bad! The somewhat limited range of the standard chanter (the pipe you "play" while the others are merely drones) seems like it would limit your options, and after checking out two or more more videos from these guys, that seemed to be true, yet at the same time I was impressed at how well they cast it into different keys by what the rest of the band was playing. Also, different tempos and stuff helped. I'm a fan of neither bagpipes nor metal, but this was some pretty cool stuff.