I have had good experiences with Quadratec (had some products bought there act up, and they are always very fast in getting the problem fixed). Also, their order tracking is top notch.
Delta Current Control (the guys who make my e-fan automatic speed controller) are also top notch. It takes them a bit to get the controller shipped (they were clear about this upfront), but the guy I talked to (Brian Baskin) went so far as to make a specific schematic of the electrical connection I needed for my rig to achieve what I wanted to achieve in the first place.
TCG were also very good; the inertia ring I ordered got here pretty fast... The installing of it by me, however, has taken MUUUCH longer! LOL! I received it about a year ago and have yet to install it!
radiatorexpress.com is another good example in my case; they took all my questions (e-mail and phone) and were clear about what product they were providing and how it was constructed and explained the fit.
I dont remember the name of the company, but the guys I got my brake pads and rotors from were also quite good. I may just need to find their name, as I would surely like to do business with them again!
Felipe