I've heard and read a lot of feedback that say the classic/traditional COD modes don't work very well with the maps and general gameplay design. Matches certainly don't look like they flow very well either from the footage I've watched - spawn, die, spawn, die, spawn, die etc... and the maps have a very limited and linear design.
One video I watched said that AR's a absolutely useless as is ranged combat as you're shooting a whole clip into someone trying to land bullets against someone and all they do is cover-heal and then it's back to square one. SMG's seem to be the only viable gun aside from close-ranged sniping (quickscoping) because of poor sight lines, high health compounded with dodgy bullet detection.
Double kills seem to be rare unless you camp and pray you don't have someone spawn behind you.