To join in the reminiscences over the work of Dr. J. Eric Holmes: I learned AD&D as my first system and ran a campaign from the DMG "as written" in high school, taking very seriously everything about the holy standard rules, drawing dungeons that filled up a whole sheet of graph paper, packed with a dazzling variety of monsters, and meticulously detailed with randomly rolled dungeon dressing.
What really opened my mind was the improvisational advice to DMs and the Tower of Zenopus adventure. It was spacious, not packed. It was stocked with focal puzzles, tricks, and features, not useless atmosphere. Its encounters put well-known critters in interesting situations, showing that a good adventure could be had without digging into the Fiend Folio (maybe another reason for the overthrow of my campaign). Most of all, it was described concisely so a large variety of possible situations could be shown.
Just that one example improved my DM craft, and indirectly led to my favoring more improvised scenarios and systems in college - and of course, my fascination with the spirit of original D&D now. So that's my toast to the good Professor.