I've played the series since launch. Loved D1 and D2. D3 was pretty but I didn't like how they simplified everything. It looks like they're taking it back more in line with D2's character builds, though I haven't really tracked the development or played it at all.
I will buy it probably a couple of weeks after it launches, as I got burned by their stupid 'online-only' policy on D3 and could barely play the first couple of days due to issues with their servers.
I expect it will be fun, but I am not looking forward to being forced to group with random dipshits with little to no social skills to try and clear content.