One of the very first indications that Activision/Blizzard would release this clusterf*ck of a disappointment was waaay back when we first started getting info about the game's "new art direction" I seem to remember that not only was there a petition signed by many thousands of people to stick to the more dark/gritty/creepy/gothic feel of the original Diablo (and to a lesser degree Diablo II), but also that Brian Morrisroe, the art director for Diablo III resigned at some point. Blizzard have denied that it was partly or largely due to fan outrage at the new "artistic direction".
Those and other events in the development cycle of the game made me a bit uneasy and nervous that somehow Activision/Blizzard would find a way to royally f*ck up one of my favorite games of all time. Add in their inevitably understandable decision to "borrow" ideas from their cash cow WoW, and you had a recipe for a train wreck.
Throw on top of that a shallow and transparent storyline, the indescribable idiocy of the decision to force "always online" even for single player, and a clearly rushed-out-the-door (ironically given Blizzard's fierce stance on not releasing games "before they are ready") RMAH, coupled to the fact, as many posters have said, that good drops are barely non-existent, and it really just enforces the utter disappointment and letdown that most loyal fans of Diablo are feeling, given that they have waited 10 years for Diablo III.
It's clear that Blizzard forgot all about its fans, and has geared this game to Wow-like players and to people new to the Diablo series that have no metric for comparison and thus have no idea how far Blizzard has run this title into the ground.
I had more than a few early warning signs that this would be the case, but like a kid at Christmas, I was waiting, and hoping that when I unpacked that box and started playing, it would be everything I imagined. Against my better judgment, I picked up the game, (Collector's Edition no less), and promptly quit playing after about two weeks, as the disappointment and the letdown was just too much.
Thanks Blizzard for Diablo, Diablo II, and Lord of Destruction. You can keep Diablo III, and farewell. You used to be my favorite game publisher. If there is a Diablo IV, (I hope to the High Heavens not), then it can rot in the Burning Hells.