I think the jumping arguement is Halo2's greatest weakness.  I HATE playing halo 2 online because people are just constantly jumping all over the place!  Really annoying.  You wouldn't jump in real life, therefore no jumping in GOW.

I'll give matchmaking to Halo 2, but even then, online play in Halo 2 is way too frustrating for anyone who hasn'y been playing everyday for the last 3 years.