C-130 - the first flight I ever had was in a C-130. I almost threw up, and I had taken two dramamine before taking off. It was ugly. The second time I was in a C-130 I didn't get quite so bad, but it was still a very unpleasant experience. It's dark, you sit in a web seat, you're cramped, overall completely unenjoyable.
C-5 - the only time I flew in a C-5, I DID throw up. For about forty five minutes. That was an unpleasant experience, probably the worst experience I've ever had in my entire life. And I wasn't the only one, about thirty people on my flight lost it, two in the bathroom and the rest in air sickness bags. You sit in the tail section, facing backwards, so your inner ear is all sorts of messed up when the plane refuels. According to the airman in the cabin, it was the worst re-fuel he had ever encountered. Didn't make me feel better.
C-17 - definitely the most enjoyable plane flight I've ever had. It was still loud, but there was space, it felt almost clean, and it was a real seat. Granted, a 1950's era place seat, but a real seat. Luckily I was on the side of the plane and not on one of the pallets they assemble in the middle, cause those kept rocking back and forth with the plane, and that might have given me issues.
UH-60 - a dream. It was a bit loud, and a bit scary walking out under the rotors (I kept trying to remember whether you were supposed to approach it from the front or the side, but since we got in from the side and walked out from the front, I guess it wasn't that big of an issue), but once in and lifting off, the only thing I can compare it to is the skyride at your local theme park. Not as much shaking as I would have expected, and even the takeoff and landing were reminiscent of the little clunks as the skyride car comes in and goes through the gear things across the top.