I always seem to be in a very small minority, but I think the Pendolinos and Voyagers have aged remarkably well. If you did a random survey asking people how old they are I bet few would say nearly 20 years. They still look and feel modern. (The HST, while a brilliant design I'm going to miss a lot, wouldn't have fooled many into think it was a new train at 20!)
The interiors are mostly fine for long distance trains - nicely subdued and quite relaxing. The worst parts are, as ever, the enormous window pillars and thick wall panelling on Pendolinos. I can't see any refurbishment ever being able to do much about that - window seats will continue to be armrest-less and I'll still make a beeline for a seat with enough of a window to use the sill as an armrest.