Marillion good call on A.D.O.M. Not exactly high-tech, but an incredibly varied, extremely difficult but rich CRPG experience. The ASCII graphics are kind of a downer, though.
A similarly complex product, also free, called Ragnarok, has a mouse driven interface, automapping, notes, quests, relics, etc. etc. and it looked pretty cool. In any case, that one's at:
http://www.win.tue.nl/games/roguelike/ragnarok/
[This message has been edited by Sir Markus (edited 03-07-2001).]