From: http://www.uq.edu.au/~cswallis/nhqt/

NetHack is a Free graphical one-player roleplaying game with a
highly modular window system interface supporting TTY, VGA, Mac,
Amiga, and other displays. Qt is a graphical user interface toolkit.
So, "NetHack with Qt interface" is a version of NetHack which has
a user interface module written using the Qt toolkit.

The Qt interface has these extra features: 

o   Tiles (graphics) in the inventory and other item-menu windows. 
o   The player cursor changes colour as your relative hit-points drop. 
o   The message window greys-out older message. 
o   The item menus allow a count (click to left of icon - hidden feature). 
o   Icons for the major attributes and player states. 
o   Menus (only needed by newbie dungeon fodder). 
o   Variable size fonts and tiles. 
o   More space for the map as messages and status are side-by-side. 
o   You rarely need to put the mouse in a pop-up to interact with it. 
o   Macros - hidden feature - F1=multi-rest F2=multi-search F3=try-it 
o   It is much easier to code, so new feature-requests are more easily done. 
o   Sound support.