GSP is the obvious outlier when it comes to this.
Canada has often times been called the mecca of MMA, and GSP is one of the biggest stars in the sport and is Canadian. It only makes sense to sell his fights in Montreal or Toronto where they will sell a ton of tickets.
I think fans make a bigger deal out of this than the fighters. The opponents do not lose a day of training when traveling, as per the TS comments. Their camp is long complete, the only downside is the travel time. They wouldn't be using that time for any sort of rigorous training, only resting or maybe discussing final strategies. The Condit vs. GSP specials on UFC.com showed Condit using the time to watch more video. He wouldn't have been in the gym sparring if GSP was flying to New Mexico to fight there.
Add to that, I don't think the fighters feel any more or less capable, or at any more of an advantage/disadvantage if they are fighting on "home soil". Once the cage door closes, and the bell rings there's only one thing on their minds. You think they hear the cheers and boos? If they do, you think that's going to help them (t)ko or submit somebody? Again, the fans make a much bigger deal out of it than the fighters. I don't believe in any sort of "home court" advantage in fighting.