Diablo III is not an MMO by any stretch of the imagination, but it certainly has some strong online elements like previous installments. It also has a lot of expectations to live up to, several of which are discussed in a recent PC Gamer interview with Wyatt Cheng and Andrew Chambers. Both designers discuss the challenge level of the new Inferno difficulty, which is aimed at max-level characters in good gear who have already completed the Hell difficulty level. They confirm that while it's meant to be brutal, it can be played and beaten solo -- although having a friend won't hurt.
And speaking of getting by with a bit of help from one's friends, Cheng and Chambers both agree that twinking out new characters is a time-honored part of the game's tradition; their job as designers requires them to find ways to ensure that twinking is a fun process for players. It's the sort of interview that can leave fans wanting more of the game before it's released -- which ties in nicely to the fact that you can pre-order the Book of Cain (a collection of in-universe lore and artwork) on Amazon right now. And you can even take a look past the break to see what the book looks like.