If the demo's anything to go by 3d is a must all the time because without it I've noticed its quite hard to judge spacing etc between player and monster. Drawback being frame rate is reduced.
Used to have all kinds of visual tricks memorized for this, angles of monsters legs compared to hunter etc... After a while it became second nature and I didnt think about it anymore, and then once the series went 3d, I did a complete brain dump on it all.
For charge axe users wanting to go element up, but not wanting to waste phials getting to the super swing, if you have your axe out, simply pressing both attack buttons at the same time will start the super slam immediately, to which you can element up by pressing R, getting all phials stored into element up.