I ran across the current edition of Delving Deeper on the web a few weeks ago, and it prompted me to reread it in some depth. (It had been some time since I read my copy of the Delving Deeper box set.) The current version of the Delving Deeper Reference Rules (V4) is available online in hypertext or for free download as three digest-sized booklets.
I've decided I like this rule set very much. It really seems to reflect the rules of the original 3 Little Brown Books of Original D&D very well, and I can see that there are enough differences from, say, the Labyrinth Lord rules that I have been using, to make it a different experience. I'm looking forward to trying it out.
It prompted me to sit down and draw out a dungeon level and fill it using the method in Delving Deeper, which turned out to be good fun.