Thanks Aaron. BTW - if you go to the Kerkythea website....all the materials in the kerkythea repository will work with Twilight as well. Twilight is essentially Kerkythea integrated into SU. There is also a material library that comes with the the program, as well as templates which will give you a starting point to quickly make your own materials. Certain things, like a translucent material, will automatically get translated into a glass material when you render in Twilight.
Personally, I don't spend too much time fussing with materials. Usually, I will drop a bump map (normal map) in with any stone, paver, mulch grass etc...I'll tweak water and glass and add reflection values to any metals, like grills, etc. Other than that I don't spend too much time with all the possible material tweaking. For my bump (normal) and displacement maps, I use a program called Pixplant for photoshop. I can take any texture and make it seamless, then instantly generate my maps. Only takes a few minutes.