I just finished 6th form.
AS levels are pretty hard, at first because Gcse never had much focus on analysis, evaluation these skills are heavily focused upon at A level. So if you pick them up quickly, you will be fine.
A2 is where everything counts, forget your AS scores, your final grade is important and A2 is where everything begins to get a little bit harder and you need to be very focused because gaining marks at A2 is very hard, whatever subject you do.
If your aiming for the highest grades, i reckon hard work can get you there, but what i did notice, is that those who did best in their classes were those who actually loved the subject, the passion was there. This makes it easier for one to revise through the dull topics and still maintain focus.
gd luck everyone.