Xenosaga itself has largely been a mixed bag. All of the characters with the exception of Shion were excellent. And even at her worst, Shion was never a terrible character. Problem with the series is the story is so pretentious and detailed is virtually impossible for any casual fans to pick it up. Even standard jRPG players have trouble with the game. (Although they have trouble playing anything that doesn't say "Final Fantasy" on the title.) And old Xenogears fans shun the games like crazy. Going as far as to pretend they don't even exist.The sexiest part about KOS MOS is her heels. She does battle in sexy heels and it's awesome. Not that I've ever seen the Xenosaga show or played the games, but I know awesome when I see it.
On the bright side, KOS MOS is a very popular character even with people who haven't played the games. She's arguably one of Namco's most known characters now. And I gauruntee you only about 1/3 of the fans actually know anything about Xenosaga.
But hey, EGM rumored recenetly that KOS MOS may get her own action spin off game. If she does, you can bet i'll be first in line for it.