One of my monitors is a touchscreen Acer. It supports multitouch and I added the MS multitouch doodads.
Technically, it works just fine. In reality, the fact that the screen is vertical is a problem: it's difficult to touch the screen fast but gently, and I'm touching with the tip of the finger rather than the ball, so it can be tiring. Things are much better if I lay the screen flat, but that's not so useful in other ways...
The only time I really use it is when going through photos, some web stuff, Google Earth and for working out odd kanji, etc.
I also have a touchscreen on a little Kohjinsha notebook/tablet convertible, and I use that way more: taking notes with diagrams for example.
Tangentially, on both machines, I use the voice recognition quite a bit.