Is the AK-47 on Modern Warfare 2 a good gun to use?  

I think your to young to be playing that game if you have to come online and ask what gun to use.

By now you should know that it's not the gun that makes you a good player,
It the players that make the guns so damn good.

The question you need to ask yourself is, what kind of style and game play you like.
Different online matches need different gear, but your style of play is not going to be the same as mine.

I mean I personally stick to the ground wars games (domination & team deathmatch)
and I mainly stick with the light machine guns, since they hold lots of ammunition, and shoot fast and blow through walls.

Then I stick with smoke nads, to stay hidden and move.

to me the AK-47 is an ok gun in modern-warfare-2 after seeing all the other cool lookin gunz im not shure if im going to use it in the first one heck ya ill use it but now not so much

yes ts the great one for me i love ak47

Since the AK-47 will be awarded once you reach the last level (level 70), I don't think its not good enough to even bother with it anymore. For me, there are other better guns than the AK-47. For the Assault rifles, there's the SCAR-H. For the Submachine guns, there's the UMP and for the light machineguns, there's the AUG HBAR.

Of course, these are just my opinions.

The best assualt rifle in the game is probably the ACR with read dot sight and the slight-of-hand perk. It's not the most powerful gun in the category but it has very little recoil so you get a higher hit percentage to make up for it. Combine that with the stopping power perk and ninja pro and you'll be a force.