I have an AC-12. have had it for the past 3 years.
it has horrible wind noise. and I get this cross wind action inside the helmet and it dries my eyes out.
The visor is really hard to open now too.
I cant really tell if the vents work that well either.

but other than that its been a pretty good helmet. the padding is removable and comes in different thicknesses. Ill be buying a new helmet soon though, the visor thing is just plain annoying now.