Combat is a fairly simple matter, with only two mouse buttons and four hotkeys to worry about. Skills can be modified with runes and hotkeys reassigned with relative ease, so it is easy to test different combinations in combat without having to unlearn skills. I only ran into trouble when I was overwhelmed by numbers or tried to go toe-to-toe with a group of mobs or a boss when I should have been kiting or moving to wait for a skill cool down. In fact, some of the boss fights were easier than the Champion groups or Elite individual mobs I ran into while exploring.
At no point in the game did I get a sense of been-there, done-that to the point of tedium, at least in my initial run through the game. Once you pick up a different class, or choose to go through the game at the next difficulty level, that feeling can creep up, but by virtue of the random generation of dungeons and encounters, a new play though is never exactly the same. And each class has new skills to learn and new angles from which to view the story as a participant observer.
The only spot where the randomness caused a problem is the magic gear dropped from monsters, or the magic imbued on crafted items I was able to create at the blacksmith. There are so many stats and abilities that can be placed on items that finding one suited to my needs was fairly easy, but I found that I could never get a rare item that didn't have a wasted stat or two. I was able to complete the game with relatively few deaths, but heading into Nightmare difficulty demanded an upgrade in gear and that was something that wasn't easy to do under the find-and-equip or create-and-equip system in the game.
Enter the auction house (AH), a new addition to the Diablo franchise and plundered from World of Warcraft because of its success as almost a game unto itself. At first, I found the AH a bit awkward. Trying to find items specifically suited to my class with no wasted stats was cumbersome, but the more I played with it and found how to refine my searches, it became a bit easier, to the point that I was able to upgrade my gear so much (at relatively bargain prices) that I am now navigating Nightmare difficulty with relative ease. The Auction House still has some minor issues as bids and buyouts can timeout, which apparently occurs when a buyout is attempted on an item that is being purchased by someone else and the server is processing the request. Blizzard continues to play with it and, at this writing, the AH is down for maintenance.
Some of the battles in the game offer a huge adrenaline rush
While Diablo III had
The jeweler Covetous Shen can remove gems from your old gear