I've been mulling over windows as well. I want to do it myself, and get the replacement remodel kind where you just remove the old sashes and dividers and put the new frames and some insulation in. This makes the opening about 2 inches smaller in each direction, but it's less demo work and less finish carpentry.
I've been trying to do some research to decide which company I want to go with, but boy, is it a lot to digest. You've got:
-style of window
-frame materials
-frame construction features (which is a big category by itself)
-types of glass
-types of glass coatings (gotta check those U factors and SHGC ratings)
-types of gas between panes
-number of panes
-fake muntin bars or not
-brand
-local availability/shipping costs
-warrantee
-and price to consider.
I was planning on ordering a couple and installing them to see what they were like, and then getting more if I like them.
I'm seriously interested in
buying online from Window E-Store and getting their vinyl triple pane ECO
Xtreme windows. The specs are very good, but I'd love to look at one in person. Anyway, they go for $535 each in the size I need with the options I want. Free "delivery" if I pick up from a building supply place just outside the Beltway.