I use to play Halo 2 on the xbox all the time but PC seems to be an entirely different critter all together. I wish that there were enough players to add some sort of rank system to the MP. Most people here having been playing H2 on pc sense is was new and are really good. It gets frustrating getting killed constantly. However I really love halo and I am willing to put in some practice to get better.
Again, Welcome to the H2PC community!
And yeah Halo 2 PC is a whole different world to H2X, but its not that bad to relearn everything (as its the same)
Timings for everything will be off, so again, relearn everything