In standard class, I find the voyagers better than the pendolinos (I hate the lack of armrest on the window seats of the pendos). The windows are far better too. (First class they're pretty similar to each other IMO.) I've never been particularly bothered by engine noise/vibration, as some people on here are.
I think the standard class seating in both of them is less good than some other trains though. The London Midland 350s (at least, the ones that have 2+2 seating rather than 2+3) are more comfortable and have more legroom.
The main downside of voyagers is that they've become associated with overcrowding for me. I'm used to the Cross Country Manchester to Southampton service, and the trains are never long enough for the number of passengers. Back before they fixed the loos the smell in the vestibules was also an issue (and the problems combined, because it was much more likely you'd have to stand in a vestibule), but that issue seems to have been solved now.
If the voyagers were all 7-10 car, and the standard class seating was slightly better, I think I'd quite like them
Amy