I've got 3 of the on/off units and a couple of dimmers. They do interfere with the TV for some reason, but it's a momentary glitch only when actually using the remote.
I think they're pretty handy for controlling sockets that are difficult to get to (lamps plugged in behind sofas etc). The range of the wireless seems pretty good, but I've not really done any testing to see how far it would work from. Generally, I don't often want to switch something on or off unless I'm the room.