I had one about five years ago. I got rid of it because it was more annoying than suitable for the purpose it served. These things seem to be a constant source of stress for everyone I know who has ever had one - and I know that I'm more relaxed without mine. I tend to agree with Allister, these things are extremely annoying in public.
I think there will eventually come a time when having a mobile phone go off in the wrong place will be considered socially unacceptable in the same way that smoking is in many places.
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I am clinically insane. I am proud of it.
That is all.