I take Law A level.
My advice would be definitely take the subject if you are interested in it! In fact, I will be applying to do a Law degree next year largely because I have found it interesting at A level.
I'm not really sure why it is labelled a mickey mouse subject by some on these forums and I'm not really sure whether it is just their opinion, as I haven't heard any universities specifically slate the subject. Law, in my experience, started off as the hardest AS level I was doing (My other subjects are: 16th Century History, Geography and English Literature and Language) and some in the class actually dropped it quite early on. This is simply because having just come out of gcses - it is extremely daunting to be faced with the doctrine of precedent, pieces of legislation and latin words. However, once you get used to it it does get easier and with modules such as Legal Personel you can see why some may label it a 'mickey mouse subject'. Though, in my opinion, other than legal personel stuff - it is quite an academic subject and I can safely say that I have done more work for Law than I have for any other subject.
So yes definitely take it. It isn't a mickey mouse subject and it isn't as easy as some people might think.
NB: I just found out the Law A level will change, starting from next year, and you will need to know less information and will be able to draw diagrams in the exam...So maybe everything I said above wont apply to you and it really will be a piece of cake....