Permanent Internet connection required: So-long many forms of LAN play, or playing on a laptop in various locations without WiFi access. Like with SC2 this 'feature' is just an online form of DRM I suspect, making it more difficult for people to play the game via piracy. Alas this may also encourage certain folks to crack their copies of the game in some fashion in order to play. Sure there are lots of (vile) ways Blizzard could make this feature more annoying and less-easy to get around, but I do not feel like sharing.
No modding: Not a big deal for me really. Feel free to have a different opinion. This is only a big no from Blizzard due to the mandatory online bit of course.
Using cash to buy items: This sucks. I am not fond of cash shops for MMOs in general or pay-for DLC much of the time. I am really starting to get sick of seeing this creeping into standard gaming fare.