This is an initial review and I will probably come back and modify it.
It is fun. Is it $75 fun? I would say no. I wish I had paid maybe $40 for it.
The actual gameplay, while fun, is nothing new. We've been playing this same game for years now. In all fairness, there isn't much one can do to innovate in the hack-and-slash format.
Why does it make you wait so long to get a mount? Seems odd.
The gameplay loop is already starting to grow stale and I'm not even done with the story. The dungeons have gotten repetitive and some of them feel like they were almost copy-pasted. I know a few people who finished the story and were so bored with the gameplay by that point they quit because the story was the only thing keeping them engaged.
The graphics also have not really impressed me much, the cinematic scenes excluded (those are the usual Blizzard awesome). My wife saw my screen and thought I was playing Path of Exile and I haven't been able to get that out of my head. It looks basically the same.
The story is good. I am quite enjoying it. The voice acting is so great. It is way better than D3 in this regard. I haven't completed the story yet, so no spoilers please.
They did not learn from the beta and Druids need a heavy early-game overhaul. Yes, they are effective later, but they have to go through hell (pun intended) to get there. Bosses that took me 5 minutes on my Druid took me like 10 seconds on my Rogue. They also force Druids to hike to the other side of the freaking map and beat a bloody stronghold to get their class specialization, whereas with the Rogue it was a short questline in the first area and I had it. Druids need a major early-game buff and a class quest that is far more accessible.
I don't like how the Paragon system is presented after 50. You get an XP bar and every 25% you get another point. I would prefer the D3 method of presenting it: an XP bar that fills all the way for each point. Yes, nothing would functionally change, but it would feel better to be seeing that XP bar move rather than the microscopic increases it gets now. It makes me feel like I'm wasting my time as it is right now.
The legendaries have been a lot of fun to find. The buffs they provide really do encourage you to shake things up with your spec.
I love how easy it is to respec. If you sell your gear, the respec cost quickly becomes irrelevant. That being said, I honestly don't understand the purpose in the gold cost for it.
We'll see what the endgame ends up looking like.
Update:
The post-story stuff is fun until you hit a wall. Leveling slows down to a bloody crawl. At first, you are getting new and cool gear and it is fun, but then that just suddenly stops. All the stuff dropping becomes worthless. You get uniques, but the affixes on them are pointless. You can do nightmare dungeons, but don't expect anything even decent to drop.
I did the dungeon to unlock World Tier 4. Glass Cannon doesn't even begin to describe what I am there. I can kill things fast but even a slight breeze kills me.
Honestly, thinking of uninstalling until some big changes are made. The post-story is just simply bleh right now.