DIABLO 3
THE GOOD
The first time you play it up to max level, you're going to have immense fun learning the spells, skills and enemies. This takes about 10 hours. After max level, you'll soon realize just how empty this game is. With 5 character classes, you can tinker with the styles, the spells, the skills, and how much fun you'll have playing each. I, personally, like the witch doctor the best.
THE NOT SO GOOD
Then, the 'difficulty' ramps up. It's okay into the middle levels (nightmare mode) because the game is fairly balanced about it, and you're still 'fresh' with the game. Basically, the game adds exponentially more and more hp to enemies, some with special skills that are basically immune to specific playstyles/hero types. This is fun still until it is no longer fun. At the point where it is no longer fun/impossible to progress, you have one of two choices: try to whittle down the enemies with friends in game, or run/leave game/repeat until you get an easier instance of the game.
There is nothing 'new' at higher difficulties. There is no new item system. There is no high level crafting worth anything. Loot drops at the highest level are the same blandness level at 'growing' levels (read: fucking bland). Speaking of the weapon system, the entire premise of the game is built on 5 classes, all of which rely on the same stat build: weapon damage
THE WORST PART
Let that sink in for a minute. Every single character class is dependent on weapon damage to succeed. INT? no. STR? no. ATTACK SPEED? it used to be a 'way to go' until it was nerfed. Now it's just... a good bonus. Literally, the only stat you are ALLOWED to care about in order to trudge through areas is weapon damage. A wizard using a high damage sword is better than using a staff, provided that the sword does more damage. What is the real world effect on this? Every single player is seeking out the highest damage weapons, inflating the value of those items immensely. Also, there's no "other way to play the game" or item builds worth trying. Like, you can kind of build a defense-based witch doctor, but it's not really effective, and that's about it.
Since high levels add exponential HP to enemies, you literally need more and more damage in order to do anything. How do you do more damage? Weapon damage. It's the only way to add damage to your spells, skills, melee attacks... to anything. That 900 damage two-handed sword is in your list of goals as a witch doctor, even though your character shoots poison darts (that makes sense...).
The game was more fun at one point (read: the first month of the game's release) when you could farm gold 'against Blizzard's original plan'. Since the game came with an auction house, Blizzard had decided that they want to funnel all high level activity into it, to make more cash for themselves (I presume).
Do you guys know Candy Crush? It's the exact same premise in both games. The early levels of Candy Crush are a great little time waster puzzle game. Then, the game lies to you somewhere around level 50 or 60, appearing to be the same game, but making it impossible to progress without paying for items. Diablo 3 is exactly the same thing. You simply can't play high level stuff (read: after 10 hours of play or so) without using the Auction House.
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Now, all of this 'beat em up' style gameplay is really smooth, and it follows a really boring weapon system. It could be remedied if the dungeons and open areas that you can play in which are fun and enjoyable. What about those, you ask?
Well, ACT 1 is roughly 40% of the entire game in terms of length. It is the most enjoyable for me, personally, and each following ACT becomes less and less enjoyable IMHO. The kicker is that this game provides zero random instances/areas. In other words, you will be playing the same area over and over and over and over until your weapon damage is high enough to move onto the next area.... to build up your weapon damage... to move onto the next area, repeat ad nauseum.
There is nothing else to really do after you hit max level. You simply try to get the highest level (FUN, to learn the game, enjoy the mechanics, play different classes, etc), then, try to get stronger (not fun AT ALL, for reasons mentioned earlier).
All in all, it's fun to play for a little while, but then becomes an exercise in frustration. It is not worth playing for any length of time, in my humble opinion. But, it's still worth playing in the early game.
I really do wonder how the game will play without an Auction House on the consoles