I've been running AD&D using the original three books + Unearthed Arcana for just over a year now.
One PC has already changed sex thanks to a cursed magical mask (which also turned him into a would-be serial killer of orphans, also, a healer of the blind). Another PC has the soul of an ancient Dragonborn inventor stuck in him, plus a few odd high-tech items, like a Gravatic Staff and a "Walking Chair".
The swashbuckling caveman has acquired a magic sword, an 11-year old paladin sidekick, and rescued a moose who's really a reincarnated, philandering Grand Druid.
The party magic-user just cast his first fireball, setting a neighborhood on fire, in addition to a brother and sister pair of slavers. He's now wearing the brother's Ring of Shooting Stars. I'm sure more property damage will ensue.
Oh, and the group as a whole has pissed off an embassy full of elves. Campaign's going fine!