Whenever I jumpseat (which was a lot) I go out of my way to say hi to the FO and shake his hand. Mainly because I know I like anyone JSing when I'm the FO to say hi...but it's no biggie. I had a pretty senior DAL guy sitting in the jumpseat a few months ago (somewhere in the low 60's on their seniority list) and he was awesome. Chatted with me and the CA the whole time (out of sterile cockpit of course) and was very friendly despite being crammed in the 145 jumpseat. Just depends on who ya get I guess.
At the same time, I have seen a DAL guy exhibit a lot of animosity towards a CMR guy when me and a CMR CA were both trying to jumpseat. It's none of my business so I stayed out of it. Long story short, the DAL CA tried to put me in the JS before the CMR guy (even though they have priority) since I was there first. In the end, we both got seats in the back thanks to misconnects but it was definately a little uncomfortable at the gate.