I was reading PC Powerplay Issue#155 the other day and it talked about how many Blizzard fans rejected Diablo II and told Blizzard to change them.
Personally, i believe that's crap; the guys at Blizzard are veterans and veterans only. The Lead designers are the best on the market, as are the graphics and artist guys. The guys might be new to Blizzard, but that doesn't matter. Blizzard was new to the game industry and came up with StarCraft and WarCraft without the need for fans to play a part in the design process.
Diablo III is clearly in a later infantile stage; whereas the ability to show off the game is active but its clear that Diablo III won't be released for at least another year so my opinion is that people should just wait. If theres something you like; Great. If theres something you don't you like, Don't worry they'll probably change it.
Blizzard are Professionals and i say we leave it to them. But thats just my opinion, other people may like to be involved.