I've had one of the ESU 50200 ECoS command stations for about 9 years for an indoor HO layout and added a Mobile Control II handset last year. I've been very happy with both. I would have bought ECoS for my outdoor garden scale layout, but wanted to use battery power instead of track power and couldn't figure out how to integrate it into a that easily. (So I bought Revolution DCC instead for the garden. I've been pretty happy with that so far.) I was also a bit disappointed that the ESU CabControl systems can't do as much, for example shuttle mode, as ECoS systems. I would have wanted another ECoS system.
Greg's right about one hand use. There's a lot that you can do with one hand, but I often find myself having to use a second hand for more complicated interactions with the handset via the touch screen.