I was one of the last of my friends to get a computer and a cell phone, but now I don't know what I would do without them. I try to be polite when using the phone. If I am in a restaurant or store, I will usually go outside, unless the call has to do with what I'm buying, like at the grocery. I am annoyed by people that wear the blue-tooth and have loud conversations---likewise people who answer their phones at inappropriate times (unless they're a surgeon or something when it's an important call!)
Since I free-lance and work at different places or out-of-town, (and I'm usually rarely home until 11PM) a cell phone is a necessary evil.