Voted "not at all" which is true for my current life. My current job is not great, but I have two colleagues whom I really like, and that's all I need in respect to loneliness, at least.
The one period in my life when I felt really lonely was some years ago when I moved to another town for a job. I just couldn't get a good contact to my colleagues at all. Eventually it turned out that there were conflicts in that place between different groups of people, and that the boss made it all worse. He may well have tried to use me to get other people to work harder, resulting in resentment against me before I even arrived. Anyway, they all made it clear, without really saying it, that they didn't need me around.
I left there in a hurry as soon as my contract ran out. The next place was weird, so I fitted in much better .