If you look at the list of fics on the trek_news comm each day they're about neck and neck in numbers of fics, but I'm a total S/U fan. It's gotta be a superior fic to get me reading K/S, though I do like Kirk/Spock Prime.

I've been impressed with the quality of the fic on the spock_uhura comm, too. For such a suddenly huge fandom it's attracting some excellent writers. Coming from the Buffy fandom where 95% of the fics are crap and the writers can't write, I've only found this case of quality in small fandoms before.