I used to swear by Gator Skins.
I have not felt any slower on the ribmo's, and I went from 23 Gators to 28's in the ribmo's.

I've also used Panaracer Pasala's same tread as the T-servs, just different compounds.
I liked them as well, but they wore down pretty fast when skipping and skidding and the side wall started to give out. Seems they answered those problems with the t-servs though.
And a hand full other tires that I would not recommend.