I use two Samsung TVs both with Keytec overlays. They seem to work pretty well although calibrating them can be a bit tricky since I use them in portrait.
I sometimes think about replacing them with dedicated touchscreen monitors as I think they might be a bit easier to use. The touch is generally reliable but sometimes it doesn't always register and the overlays mean that the monitors sit some way behind the touch sensitive panel. Other than that, they have worked well for me.