1. Only real pitfalls I can think of are people not properly securing the tubing on the barbs and not doing proper leak testing. This can be avoiding by having a little patience, and using zip ties/clamps/compression fittings.
2. My general rule of thumb for companies to stay away from: Koolance, Zalman, Innovatek, Thermaltake. Just stick with the good companies like D-Tek, Swiftech, Danger Den, EK, and XSPC (just to name a few) and you'll be fine.
3. In general, most people call single 120mm fans 120.1, and dual 120mm fan rads 120.2's. Etc etc. It all depends on your heat load, but I never recommend getting a single fan rad. Considering you can usually get a dual fan rad for like 10 bucks more than a 120.1, it's really not worth going with the 120.1. If you let me know what you plan on cooling with the loop (E8200 and 9600 GT, or what?) then I can give you a radiator recommendation.
2. My general rule of thumb for companies to stay away from: Koolance, Zalman, Innovatek, Thermaltake. Just stick with the good companies like D-Tek, Swiftech, Danger Den, EK, and XSPC (just to name a few) and you'll be fine.
3. In general, most people call single 120mm fans 120.1, and dual 120mm fan rads 120.2's. Etc etc. It all depends on your heat load, but I never recommend getting a single fan rad. Considering you can usually get a dual fan rad for like 10 bucks more than a 120.1, it's really not worth going with the 120.1. If you let me know what you plan on cooling with the loop (E8200 and 9600 GT, or what?) then I can give you a radiator recommendation.