I had one last summer. I went into it petrified - the idea of a tube going down into my lungs sounded horrible. But it really wasn't bad. They numb your nose/throat with a spray before they sedate you; that's not fun. The numbing made me feel like I was drowning in my saliva, like I couldn't swallow. It just *feels* that way, though! It helped to sit up during the numbing process - felt like I was able to swallow easier. After I was numb, they did the sedation - I really didn't feel a thing after they sedated me. It was like a general anesthetic; I guess medically I was awake, but I don't remember a thing. It was a bit wierd during the days after the procedure - I kept *thinking* that I was remembering what they'd done, but I couldn't *quite* remember. Kind of drove me nuts, wanting to remember but not being able to!
If you are nervous - I was! - tell the medical staff how you are feeling, and they'll understand - will do everything possible to make you comfortable.
No side effects, either. I came home (a friend will have to drive you home), didn't do anything major during the 24 hour period after (per the rules), but didn't feel terrible either. For all of my stewing about it before, it turned out to be a yawner of a procedure!