Style can make or break a game. Heaven knows some games that are lackluster in terms of gameplay enjoy immensely from a definitive art style, that compels the player to overlook these deficiencies in order to appreciate the visceral, the fantastical, the hypnotic and the entrancing aesthetics that engulf the game worlds, invigorate the characters, and breathe life into a universe. If Geometry Wars didn't sport retro vector graphics and bright, neon colours would it be nearly as entertaining? If Okami wasn't as beautiful would it be as popular? Art can help a game transcend the traditional benchmarks of what constitutes a 'good game.' It can be appreciated, dissected, and extolled as the pinnacle of the medium. Its what makes games unique from one another, preventing them from suffering the dreaded denotation of 'generic.'
The first two Diablo games were punctuated by a distinctly dark tone, coinciding with the Gothic theme replete with Daemons, Witchcraft and legions upon legions of Hellspawn. The games attracted a rabid fanbase, and as with any fanbase, these obdurate (but intensely loyal) Blizzard sycophants are utterly resistant to any tweaking of the precious Diablo formula. Thus, with the announcement of the long-belated Diablo 3 revealing a somewhat different tone (permeated by more a more vibrant palette) many fans were jarred to say the least. There was a public outcry, even propagating a petition to see the changes reverted and a more traditional look reinstated. Well, I say, good on Blizzard for making some much-needed augmentations to the visual style - after all, innovation never comes about if developers re-hash the same shit over and over again, playing the safe hand and not taking risks in the name of pioneering a new way to think about games. From what I've seen the sequel looks great, and I have no doubt that upon its release the rabble will be silenced when the overwhelming majority fawn over the new Diablo, much like its forebears.
The only things I'm really concerned about are the "gameplay" implications involved with a lack of light radius and new the new proposed inventory system.
The game is still a 'dungeon crawler' set in a pseudo-isometric perspective so the removal of the light radius (a trademark of the series) removes a large feeling of atmosphere.
With the new technologies, they can actually create far more pleasing effects that make maintain the colors (if not enhance their vibrancy) and still create a blanket of darkness. Here's a perfect example.
A layer of shadows (inside dungeons) and fog (for outdoor areas) can completely enhance the dark tone while maintaining (if not enhancing) the vibrant colors - as well as make things such as a rainbow become a powerful contrasting symbol.
As for the inventory issue (not art-direction related), I'll just say that the single-slot holders are great... but should only exist for the player's stash so we're not limited to storing ten items max. The inventory's micromanagement system is a major aspect of gameplay.