It's kinda like Maths in a way in that once you know a rule or a mechanism, you can apply it to any question. The only bad thing, if you're doing OCR, is that you need to know basically all of the definitions for the first module. Once you get to module 2 and 3, you basically only need to know what a nucleophile and electrophile are and then fill in the rest.
I'd go as far as to say it's probably the HARDEST A Level (At least in science) because you do need to know a lot for the exams - the modules are definitely very varied, whereas with Physics or Maths, it just flows better.
Not to discourage you, but make sure you know what you're getting into. Maths is definitely my favourite A Level, but I love applying my Chemistry knowledge where I can. I was discussing a possible hangover cure with my tutor the other day after a mate got massively rough over the weekend, and we actually sat down and went through the science making it work. Coming soon to a store near you.
Biology ******* sucks though. Unless you're lucky enough to be able to do Human Biology.