There is no native controller support, but you can use a controller (you just have to assign a function to each button manually).
In D2:ED there was a technical level cap of 60, or so, but a practical max about level 36/37 (a couple got to 40 spawning opponents at a particular location near the end of the game). In the early game leveling is faster in DKS (getting to level 9 finishing up to a certain point, rather than level 7 in D2:ED), but nobody has reported end levels yet.
You can leave the tutorial section fairly quickly, if you wish. I bought an Xbox to play D2:ED, so played around in the training area to get a feel for combat and the controller, then went through a few more times to get enough gold to buy a decent starter bow (handy through the mid game in D2:ED even without investing in any ranger skills), and then I was almost up to level 2, so kept going. Leveling goes faster once you move to Broken Valley, and start getting more than 1 exp per kill.
In D2:ED you could unlearn all your skills (for a price) starting about half way through the game, and re-invest them. The skill system has changed in DKS, but I would expect this function should still be available in some form.
Combat in D2:ED was not twitch based, but was fairly action oriented. It wasn't as strategic as a turn based system, but your approach could certainly have a big influence on combat (weapon/skill choice, use of cover, high ground, etc).
Spell casting is a button press, just like melee or ranged attacks.
Anti-aliasing works for some people/systems. Others have got it working if they disabled HDR lighting, or forced AA in the drivers (or renamed the executable to get the drivers to use an existing profile from another game). Some people were not able to get it working.
