I loved the MP5 in modern warfare last year.
This year I think it's still a good gun. It's definitely a lot smaller in size and increases your mobility.
However, when you gain one thing, you sacrifice another and this sacrifice was damage given.
Damage is ok, but takes more bullets (4-5) to kill a guy. It's mobility is great as well as the reloading time (a little more than a second). Good fire rate. The range is the only clear down side to this gun.