It can be really pleasurable.
Like anything, though, it has to be something you're in the mood for. I really enjoy it most when I'm fresh from a shower. I can get a little uncomfortable if someone goes to rim me and I haven't just came from the shower. Not that I'm dirty or anything, but the fear of being dirty keeps me from enjoying it as much as I should.
Overall though, one of my favorite things to have done, and a BJ in combination with attention to rimming can be phenomenal.