Solar installations

Does anyone here know anything about solar panel installation, especially regarding production based upon roof orientation and slope?  I think my solar installer is bullshitting me and just generally has their head up their ass and I'm trying to see whether they even did their job to evaluate my house for a larger system.

I used to do contract work for a solar mobile company and have some knowledge about install solar panels on the roof.  Here is a website with lots of good info:

http://www.solartown.com/learning/solar-panels/installing-a-solar-energy-system-yourself-knowing-what-to-buy/