A hobbyist from-scratch free-software project is a really neat way to make olde timey DOS games work again on modern computers, imo.
http://www.gamersgate.com/DD-XCOMUD/x-com-ufo-defence
http://store.steampowered.com/app/7760/
No client is required for GamersGate, but you will need to run their installer to get at the files (works in WINE though last I checked). Sadly it's not on GOG yet.
Still no keyboard controls, though.
EDIT oh, they do have keyboard shortcuts now.
I am now playing XCOM: Enemy Unknown on the iPad, even though I have the computer verion on Steam.