I'm also replacing 11 windows in my home.
I have talked to 7 sales reps and researched Milgard, Anlin, CertainTeed, Simonton and Anderson.
All of these brands look fine. Probably Anderson is the best, but you have to pay for the name. Milgard is ok, but the glass is not as dense as the others, frames are too big, windows wobble, has only single lock regardless of the size of the window, has no child safety and warrenty is not transferrable. Also they haven't improved their products for 5 years. But this is the cheapest quality window. Anlin is disigned for California. They used to make CertainTeed's winodws and have very high quality in every way. Price is also reasonable (about 10% higher than Milgard classic). However, they started making their own windows since March, 2001. My question is if this company will be there after 10 or 20 years?
I already have 2 Simonton vinyl windows in my home. These are at least 3 years old and look fine. The quqlity is also #1 in Builder's Magazine. I think Anlin is better but I just don't have guts to go for it. Also, I live in Northern Ca where Climate is extremely good. Sicne I never use air conditioner or it never snows, I don't need the best quality windows.
So I'm installing Simonton. Their web site is not very attractive or graphical but I love the quality and warrenty.
If you hear any major compalints about these brands, I believe it's not because of the windows, but becasue of the installation.
Window replacement is a big expense. You should look for a certified installer with good reference. Good luck.