I know the idea of a Comeliness stat had been booting around for some time before UA came out, largely to a general reaction of "shrug" given that it was taking the already-weakest stat in the game and cutting it in half.
That said, one short-lived game I played in actually used the 7-stat system, which I and my DM-observed dice very quickly proceeded to break the hell out of: we rolled for creature type (a.k.a. race) and after a series of outlandish rolls I ended up playing a full-blooded Dryad. I then rolled some mighty fine stats, on top of which came some crazy racial adjusts for both Cha and Com such that I ended up starting with 19s in both.
For a Dryad - who has innate charming ability - whose class (Bard, using some Dragon-Mag variant) gave her further at-will charming ability, starting with 19s in both Cha and Com was broken as squawk. I could charm the birds out of the trees, never mind charm absolutely anything that ever even thought about opposing us.
The DM wanted to run us into Village of Hommlet. Near that village is a community of about 500 Kobolds: I charmed the lot of 'em (and the party assassin quietly dealt with the very few that resisted) and sent them en masse into the dungeon ahead of us. Easiest adventure ever!
We never used Comeliness again!