My boys are night and day!
Possum is very scared, but is beginning to try to explore the room more each visit. He does try to get back into his carrier to hide, so we have to keep it shut (we have to "dump" him out, gently, to get him out.) A lot of the time he will curl up in my arms or on the table and push his face (hard) into the crook of my elbow. Fortunately, he doesn't try to bite or scratch or excessively try to get away when he has to get his temperature taken or get a shot.
When we get home he'll hide from me for a few hours, but warms up to me again quickly. He'll be a little more skittish than usual. The trip to and from are okay enough, but he doesn't like being in the carrier; I have to scoop him up calmly and quickly and put him in it. There can be no mistakes, because if there is, I probably won't get him in. He doesn't like being picked up in the first place.
The funniest thing is that the entire pitch of his voice completely changes! Normally he has a very high pitched voice, but when he gets into that carrier, his voice gets very low, and definitely not happy sounding. Seriously, he sounds like a completely different cat!
Loki on the other hand is much easier in everything. He also doesn't like being in the carrier, but you can just pop him in with very little trouble. He cries in the carrier like I'm giving him away, but once I let him out he's fine. He comes right out, doesn't try to hide in the carrier. He's completely at ease, friendly, and very inquisitive.
At the most recent trip to the vet, he acted like the room was the same as our home. He looked around, jumped from one place to another. At one point he even flopped down and laid on the floor. He doesn't bite or scratch, but you do have to hold him so he doesn't get away when the vet takes his temperature. However, he's fine with getting shots.
Loki was really funny with the vet, too. He was rubbing on him a lot, nuzzling him, and just purring the enitire time! It was really cute. He's okay when we get home, too, for the most part, though he does seem slightly wary.