It depends what board you're on. Bio and chem i'm on aqa, and it's not as bad as I thought it was going to be. There's a lot in terms of volume, but i don't find it that challenging. It's still harder thatn gcse, just saying.
Physics i'm doing advancing physics (B) with OCR and i think that's difficult mainly because the textbook's rubbish. The questions have different possible answers but they're only looking for one, so sometimes it's hard to get the marks. Again, it's not that bad. I'm dropping it next year (hopefully) but carrying on bio and chem, only dropping it because i can't do 5 a levels too much work, and because i don't like it as a subject.