The biggest letdown for me was Starscream -- those rear fins were hard as heck to move during his transformation. Then, to make matters worse, a piece of plastic broke off on one of the legs and refused to let itself be glued back on because it looks like the pin was inserted in some weird diagonal way that seems to have been the cause of the problem. Granted, that fin moves much easier now, but now I'm afraid to transform SS because I want him to at least look intact when viewed from
one angle.
For a while I was even afraid to touch Skywarp because of this problem, though a later examination of him revealed that he doesn't have this issue. So basically my SS sucked, and that is why he is my least favorite of the Classics line.

I actually kinda like Grimlock, though. Yes, the robot legs and feet could be way better, and he would've been the one voyager I would eagerly have purchased (I picked up none of the Classics voyagers save Ultra Magnus in the 2-pack and only begrudgingly got Thundercracker and Ratchet in the movie line), but I still like him enough in robot mode to display him in that form. He doesn't look so bad if you bend the knees and spread the legs when posing him.

And I agree that Prime would've been ideal with a trailer, but I'm not sure I'd miss it as much on the voyager figure. The lack of it
really hurts the deluxe version, though, since the latter half of his truck is so poor. Not that the front is exceptional by any means, but I could definitely forgive it if the legs were covered by a trailer! As it is, they're so friggin' long and high (due to the stupid kneepad thingies) that they have thus far resisted all of my attempts to fit Prime with a generic trailer from another toy/model line.