I know there are a lot of foot massage places in Vegas, but I think they are clean and the masseurs are good. I am not loyal to anyone, but so far I'm happy with all the masseurs who have worked on me. If you can't stand too much pressure, stay away from the male masseurs.
Book in advance especially on weekend or you'll end up outside which made me feel "exposed" and uncomfortable.
They could improve on their foot bath as I've been to a few in China and they always added fragrant or even Chinese herbs in the water.
I never experienced problem with tipping as I'm always quite pleased with their service. I tipped $10 for 1 hour and $15-$20 for 90 min.