well, if you're expecting to get high killstreaks or high kill to death ratio, the shield isn't really for you...usually I go 1:2...it REALLY helps if you have a teammate or two that is backing you up, sadly 90% of the time your teammates go the other way.
I like the riot shield because it's great at frustrating people, they try soooo hard to kill you, eventually some people just turn around and run the other way, that's when I pull out my shotty and blast em in the back! lol
Also a cool thing, when you have your secondary out, the shield protects your back (directly behind you, not your sides)
One game I REALLY pissed off the other team...there was a teammates sentry gun above some stairs, so I had the idea to crouch in front of it on the stairs so the fire would go over my shield, but the enemy's bullets that were trying to hit the sentry to disable it would just bounce off my sheild....I think that gun killed like 14-15 people before someone came behind and disabled it with a knife...at which point I turned around and pummeled the guy with my shield...lol.
The riot shield is awesome in narrow hallways/bunkers, not so much in the open. I'm kind of a funny player tho, I'm either REALLY defensive with my riot shield, of I go balls to the wall with Akimbo TMPs (Dual Wielding sub machine guns.)
P.S. 400th post!!