So far, it's pretty good. I haven't gotten too far, but the combat, magic, dungeon layout and religion systems all feel right to me, and seem to be deeper than Nethack's.

I'm mostly writing this, though, to share the following message sequence, which is the game's response to two of my commands (one to read a scroll, and another to look at my surroundings):

As you read the scroll, it crumbles to dust.
A horrible Thing appears!
Move the cursor around to observe a square.
Press '?' for a monster description.
Floor.
An abomination.
It is friendly.

On Twitter: @mogwai_poet