No, I would never say yes to being immortal. I'd like to live long, yes, maybe even tens of thousands of years, but I wouldn't want to be immortal. To me, it just doesn't seem that great. Yeah, the first million years might be fairly interesting, but after that, there just isn't anything you haven't already done. There are no foods you haven't tasted, no possible places you haven't visited, no stories you haven't heard a thousand times before. Maybe I'm a bit pessimistic that way, but I don't think it would be fun.
Even less so if I didn't age at all! Being on my twenties for eternity would totally suck. I want to be a writer, and some kid as a writer just doesn't feel very credible to me. Also, if I had kids, I would always look the same. Guess how much that'd freak out other kids? "Hey, you're fifteen, so how come your mom looks like she's twenty? How young was she when you were born?"
Nope, I wouldn't want to be immortal. Maybe I'm a bit weird, but eternity seems like a little too long of a lifetime for me. I'm not afraid of dying. I want it to happen one day. I don't want to live forever. It sounds pretty scary to me...
I'm writing a story, though, where a person is immortal ^-^ she's also invincible so she can't kill herself even if she wanted to. That proves to be problem for her...
Also, the manga Mermaid Saga by Rumiko Takahashi has a pretty interesting point of view to immortality. I really liked it ^-^