For us, replacing old wood windows with vinyl, was a no-brainer - and energy conservation was just a minor selling point. Did ours about 8 years ago, and I'd do it again in a second.

In addition to saving $30-50/month on heating and A/C, we gained two benefits that were worth the change, even were there no monthly savings.

Our home is now quiet - we can't hear a thing from the outside world. No more road noise, and the screaming rugrats that fill our family friendly neighborhood, no longer make me think of solutions I can't discuss here.

Second - they function just like the day they were installed. They are near impervious to heat/cold/humidity, and just plain work.

I don't doubt for a second, the experiences you've mentioned. But, there are tons of manufacturers, tons of installers, and geographic and weather concerns that don't apply to everyone. "All vinyl is bad", is simply too general a statement.