If you get the Ergons, be sure you get the ones with the alloy clamps as pictured. There is a model with "nylon composite" clamps but when I tried those they stripped out very easily. Hope you are liking your new Fairfax, I find the gears shift well if it is kept in proper adjustment. I found this video very useful, he also has one on the front derailleur.
http://bicycletutor.com/adjust-rear-derailleur
About 90% of the adjustment is having the right cable tension, once the limit stops are set right. If it doesn't shift right, often a 1/4 turn of the adjuster is all it takes. Hopefully you have a good floor pump with a gauge, I pump my tires up before each ride and set the pressure to about 80 lbs.
Oh, and as for the seat, I am having no problems with the stock WTB Speed V seat (my Fairfax is a 2009 model). I've ridden a total of around 150-200 miles on it, the longest ride being 28 miles. I keep thinking about a better seat but so far I can't find a good reason to upgrade.