We put retrofit vinyl Simonton windows from Home Depot into our 1950’s home. Had them do the labor as well. They installed 9 windows for $5000 in one day. In regard to the comments about retrofits decreasing a homes value, I think that is all in the eye of the beholder. We were more interested in functionality, our home is small, and we are not the fancy nor rich type. We simply enjoy that they do a fantastic job insulating our home and making it much more cozy. They also look way better than our old windows.
You can get a $1500 rebate check from the government if you install up to $5000 of energy efficient windows before the end of the year.
My opinion…. if you have lots of money, dont mind construction mess, and want to make your house fancy, then do the full remodel. If you want new windows to keep your house warm and to give it a quick facelift, do the retrofits.