This may confuse some but I've ended up on Voyagers a fair bit of late going to and from uni to Manchester and sometimes London. I haven't noticed the toilet smell all that much (though I seem to be immune for some reason - once travelling with my dad he thought it was me and I had to explain it to him, Voyagers being unfamiliar territory to him).
However, that's about the only positive comment I have for them. They're awfully cramped and just feel generally dirty, both atmospherically and in real terms. Underfloor engines - could be worse, at least they aren't as bad as 185s, but I still don't like them.
They're always a pain to get down the aisle, they don't always have luggage racks, sometimes there's just an empty space, and I often find myself standing in the vestibule for upwards of an hour.
I've only been using them for the past few months, but I don't think I've ever been on a Voyager, XC or VT, that's had a full compliment of working seat reservations either. I've seen screens dotted about not working, entire carriages, entire trains, systems failed to update and showing reservations for previous journeys, and screens saying seats are available when actually they aren't.
I also can't work out if Voyagers have an unreserved section or not - is it coach C?