W3bbo said:

Don't get a touchscreen for desktop use, it's a gimmick. If you want to do it properly, get a Cintiq.

Instead go get yourself a good quality 24" display, like the Apple LED Cinema Display.

I have an HP TouchSmart 22" at home.  It is most definitely NOT a gimmick.  I use it every day.  The machine has the included wireless keyboard in front of it, and I stash the mouse away since it's not needed.

Now, I don't do work on this machine.  I do light web browsing, e-mail, IM, some media playback, and that's about it.  It's on a high table by the window near my kitchen, so I'm generally standing while I use it.  I read news on it every morning and I love being able to walk up to it, tap on some links, pan through the pages, etc.  It runs in high DPI so the text is readable from a bit of distance too.  Working with a set up like that with the mouse is pretty uncomfortable and cramps my wrist.

For a workstation / typical desk set up, it may not be very useful.  But I just moved to a new (small-ish) apartment, and so I got rid of my desktop PC which I realized I was never using anymore.  When I work it's either at my office or on my laptop, and I don't really play games these days, so the TouchSmart made perfect sense and I really like how it fits into my lifestyle.

 

Oh yeah, I got mine refurbished for $900 (looks and works as brand new).