According to one of the Ohio Dreams coaches, AR50 seems like a pretty brilliant move by Armada. He was riding AR7's and JJ's all last season and will be adding some JJ AK's to his quiver, all of which feature AR50.
He feels that there is very noticeable difference in the weight/swing weight of the skis(skis with AR50 feeling lighter), however he feels they ski just as well as something that is exclusively sidewall construction. Also, despite a tip first, direct hit to some metal supports under a box, he hasn't had any issues with durability.
Hope that helps!