I would be interested in an AK in 5.56 NATO if the price was right (not very expensive). Like the poster above, I have a bunch of ARs in 5.56 and a good amount of ammo for it, so another gun that utilizes that same caliber would be useful and also fun to do comparisons. I would anticipate it being more of a range and plinking gun, but I think it would be fun and interesting. I've looked into other guns in 5.56, but generally the high cost has kept me away (SCAR, Tavor, FS2000, etc).
I have an AK in 7.62x39, but I have never considered an AR in that caliber for some reason. AK ammo is still relatively inexpensive compared to 5.56, but not like how it used to be.