Really? Man I saw lots of threads over at ar15.com about the 7.62x39 having feeding problems. I'll have to check into it again. I still like the idea of being able to shoot the cheapest centerfire ammo available in an AR platform.
If you want and AR in something other than 5.56 then i would get the .308 which is a great round if you want 7.62x39 then just get an AK, there is a reason why it hasn't changed much in 50 years!
I will say that the only reason I have a 7.62x39 AR is that the upper, a mint-condition Colt A2, was given to me by a friend. I slapped it on a RRA lower that I already had.