The server play is to force the RMAH system, not enforce DRM. If you look at the entire way the in game economy was designed its blatantly obvious; unfortunately, there's no BoP, permanently degrading equipment or any equipment sink in any manner, so having the RMAH in softcore makes no sense. Pissed me off that hardcore doesn't get one because their afraid of lawsuits.
When you disconnect it immediately tells you and there's a checkpoint at the start of every floor of every dungeon, even half way through some floors.
Health pots stop dropping after the introductory acts. Act 3 doesn't even have vendors which sell pots.
Gear is meant to be found or crafted, not bought off the NPCs.
In all Diablo and Diablo-like games you just teleport back to town and sell your loot anyways.
You unlock harder difficulties after you beat the game just like every other Diablo game made; just this time, its much easier to allow more people to get into it.
Monsters abilities get more varied the further into the game you get, again to teach new Diablo players how to play without making them rage quit.
Initially I hated the new limited skill system, but it actually opens up a lot more tactics and ease of use then D1 or 2 ever did. I just wish that if limiting to 6 skills, you got to choose which 6 out of all of them, instead of just categories.
Games like Torchlight haven't added anything new to the genre either. Diablo 3 is just a nicely polished game. Of course it has issues having just been release; but every game does.