Supposedly you shouldn't use anything but iron sights as attachments lower the accuracy for the AK. You can see it here:
http://www.youtube.com/watch?v=55c3u62xHOM (You can barely feel this problem if you just spray most of the time though.)
I just discovered the AK a few matches ago myself! I used to hate it but now it felt just fine, awesome even. And holy shit, it switches to the noobtube SO fast! I had no idea about that little perk and that just scored me a beautiful multi-kill on Favela when the whole team tried to take our flag.