This has probably been said before, but I have an XBOX and bought it for Halo. Don't get me wrong, I like PC gaming, I simply want to play a wider variety of games. To me, Halo was great for its time. However, I think that by the tijme the PC version is released (40% done after 6 months, so in another 6-8 months) it wil be surpassed by not only Unreal 2 and others, but also by its child, Halo 2.
When I first saw Halo, when it was for PC/MAC I knew that I was going to do whatever it took to play that game, but to me, Halo 2, Brute Force, Doom 3, they are all going to surpass Halo when it is released for PC. They have better graphics, more innovative gameplay, etc. I think it is a great move to port Halo to PC, but I think it would have been wiser to port Halo 2 to PC, not Halo 1. Maybe this will happen as well, but by the time Halo 2 is on PC/MAC, bigger and better things will be available (not to mention launch titles [Halo 3, anyone?] for the PS3/XBOX2/[insert-childish-nintendo-name here])
Just my 2 cents. Hope no one takes my opinion to heart.