Playing the game on Veteran is the Mutz Nutz. I can honestly say it was the most challenging game i've played. The AI is alot smarter on Vet, as it will go for head shots instead of body, will also atempt to shoot you through walls more often, uses loads more grenades and flash bangs. I can remember being taken out a few times by a sniper i could bloody see!!
I'm sure the game took me on different paths through certain levels but they just may be that i wasn't concentrating when i played it on regular.
I'm getting into the online modes now but, i admit my skills online dont match my single player qualities....plenty of practice needed.