I did AS RS this year and got an A.
Pros:
-The ethics section is really interesting, particularly applied ethics
-Unit 2, which will probably be medical ethics for you, is also very interesting
-The skills you learn, such as timed essays, independent research and making notes quickly, are very useful in other subjects
-Debating with the class is fun
-Going indepth with each topic is fun, way better than GCSE
Cons:
-Apart from the problem of evil, I found philosophy pretty boring, but that was because I had a bad teacher
-The Unit 1 exam ain't a bucket of rainbows, but if you have practice with it you'll be fine