Interesting, Idol.
Though, I had no real issues w/ the KB/mouse controls of Halo PC. This was actually something I praised about Halo -- especially on the aspects of driving the vehicles. They definitely got that right -- hey, given my complaints of the game, they have to get SOMETHING right! So, there was never a real reason for me to even try the gamepad for Halo PC. If the KB/mouse sucked or was a lil' wonky, it'd be worth trying for me.
It's just, the game itself really lost what it had going for it in the first half of the game for me, once The Flood actually began. Throw in the performance issues along w/ what I just mentioned in that last sentence and it just makes matters even worse. What was an outstanding start just fizzled out instantly in the 2nd half of the game -- except for the last few levels, pretty much.