I played the beta and I knew right away I would not buy the game.
1) Can't pick stats. This ruins the re playability of the game by destroying the hours upon hours of Research and Development to find the best builds. Instead the best builds were figured out in a matter of hours then copied. It was such a lie that 10 trillion different viable builds would be used. We all know that people copy each other. Even if one build is only .01% better people will be compelled to use it. All barbs in d3 have to use a certain few skills. Or DH any class really.
2) Not being able to name your games or talk in a chat channel. This decision is so fucked I can't even fully comprehend it. Makes the game feel cold as hell.
3) No pot chugging. I very much liked the pot chugging dynamic of d2 with full juvies etc. I thought that mechanic was fine (and so does TL2 thank god).
4) No pvp outside of town/no pvp period. I mean I have been pked in diablo 2 and been devastated but it was awesome to have hc pking there to spice it up.
5) MAPS ARE NOT RANDOM. I mean What The Fuck blizzard... I played the tl2 beta and those maps seemed wayyy more random even though they always repeat similar aspects.
6) Cannot move between acts without starting a new game. This is just plain inconvenient. Cannot mfing or play the game without repeating the same quests over and over and over including the cinematics. This is really just tedious. Diablo 2 felt atleast somewhat open.
7) You can't alt f4 or leave through the menu in a fast manner. This makes HC very unattractive to me.

It is retarded when wizards are holding big axes because wands are completely useless. Calculating attack dmg off weapons leads to goofy things. I make magical spells so let me grab this huge axe here to help me... Everyone knows including 6 year old kids that wizards hold wands... I mean come on!
9) I liked shared loot. Made it exciting. I would stop hitting ball and just start shift clicking when he was about to die hoping to grab a unique. And sometimes it worked that was fun.
I liked the graphics and atmosphere but so many crucial game mechanics were removed that it just hollowed out the game. I tried to give feedback on the beta forums but was flamed out for being one of those "idiots" who wanted to attribute stats. Everyone knows you min/max - well not me when I was 12 first playing diablo 2 and actually having fun investing time and building my frankenstien character.
BTW have you guys looked at activision-blizzard's stock price? It's only gone one way since release guess which way...
And for the people selectively forgetting d2 memory - it took a team of crazy Germans passing a barb off from one guy to the next for like 3 weeks straight chaos runs to get the first level 99 on ladder. Took Koreans like 5 days to be lvl 60 beat inferno in diablo 3. Something wrong there...
Alot of these "improvements" are blatant steps backwards... They tried to re-invent the wheel...
Here comes TL2!!!
Remember HC ironman games? Get to lvl 9 then duel to the death. So hilarious because maybe one unique would drop and one guy would have a huge advantage. That was good fun...