Once pvp is out, most complaints will be forgotten. You'll hear cries for class balancing though. Farming in D3 is just like farming in D2.
My main complaint is how boring itemization is. Main stat, vit, resist, crit/ias/crit dmg where you can get it. Glass cannons can ignore vit/resist and save some money.
Upgrades cost me upwards of 20m now and result in 20-40 stat point increases, big fucking whoop.
Not much money to be made. Gold is below $2/million so items aren't...