I've not used one (sounds awesome and exactly what i want), but to answer your question perhaps it's similar to the difference between using a mouse with a moni

I've not used one (sounds awesome and exactly what i want), but to answer your question perhaps it's similar to the difference between using a mouse with a monitor compared to directly touch interfacing with the monitor. For for example Vassal boardgame, for which I bought my Iyama touch monitor there is a real experiential difference between using a mouse and your finger for moving pieces. Less seperated and more natural.