Window World is a low-price window mass-marketer. Their lower end windows are very low end and their upper end windows are upper-mid range windows. Some franchises will provide good install/service, but others are willing to hire lower-quality install crews to keep costs down and sell at their low prices. Check with your local BBB at www.bbb.org
and be sure you view some of their recent work samples in person before you sign up, but I'd say the same about any other company you hire as well. I'd search this message board for "window world" for a sampling of past discussions as well. Good luck!