It's true to the series in that it is a game about grinding gear to improve your character.
If you don't like grinding in any game then DO NOT buy this.
Personally I enjoy the grind, I enjoy my class of Barbarian and I look forward to the PvP being added.
The story took me 20 hours on first play through which by 2012 standards is more than most AAA games, however anyone expecting a massive long 100 hour epic story is going to be sad. But that isn't what diablo is about anyway.
So far I have had issues with logging in on the first couple of days but since then it's been fine, the auction house has been fine too.
A lot of people seem to have went in to this expecting it to be an MMO and those people are bemused, most of the bad reviews are from people bemoaning the always online aspect but its 2012 and if they don't do that the game will be pirated into oblivion so what ya gonna do?
I would say that the first difficulty of the game is just too easy, i didnt even die apart from going afk to the toilet once and my friend walking away leaving me but when i was at the keyboard i did not die.
So far in the two weeks since release I have logged 50 hours, I am on the HELL difficulty now and it has definitely got harder now, I can only imagine how frustrating inferno will be.
Bottom line is, Good game if you like to grind for money/items, sadly we have no idea if PvP will be any good yet.