My ex had one, they are a bit of a gimmick but hers was a tablet laptop so was pretty good if you were on a train with not much leg room as you could have the screen flat on your lap. Very rarely used the touch screen capabilities though apart from that. Oh, it did have some pretty cool hand writing recognition software in though.
it depends what you want it for - I assume you mean a tablet PC
surveyors and estate agens use them .... as five says ... handwriting drawing ... office type stuff
games music "normal" use - well how many people do you know who has one at home (I don't know any!)
My Doctors Surgery has a touch screen to activate when you turn up for an appointment. You tap Male/Female.
Month of birth. Day etc then finally Clear screen.
Apart from the obvious hygiene problems with transmission throughout of every germ that is going around and people licking their fingers to get better contact no one seems to manage it without considerable force being used.