For your information on the tax credit here is the link:
http://www.energystar.gov/
Look lower left for tax credit info.
I printed off the requirements that were updated on Feb 20th to have them handy. There is a lot of new stuff in there and I'm sure it would be worth your while to check it out and be familar with the jargon.
Note window U factor <=.30, SHGC <=.30

Better check your P's and Q's on this. I doubt you can get a window this efficient off the shelf at Home Depot

I know the window makers have to be making a BIG stink over these new requirements. Apparently it does not matter if you live in Alaska or Tenn. this is what you get to qualify.
Ours do okay, do yours?
Your Comments????
Dave