I have an HP TX1000 that works pretty well. Probably the best thing about it is that it works fine as a conventional laptop computer, so regardless of what you decide about the utility of the tablet, you're no worse off for having chosen one if the screen is the right size for you. (The HP's is 12" and I find that size a nice compromise.)
Some of the tablet stuff takes some practice to use efficiently, and the HP puts out a lot of hot air onto your arm if you are cradling it. And the screen is not "sunlight readable" like some of the speciality (and more expensive) tablets. Like I say, though, no downside to having tablet functions,. All in all, it's kind of cool for many things, and I have recently seen opportunities to pick the HPs up for as low as $750 after discounts, which strikes me as a bargain.