I do it, and I can say that most of the things written in this thread are fairly true.
It can be quite a bit of work when it comes to revising, there are many theories and studies which you have to learn for the exam, and if you want to do well, you need to remember most, if not all of them. Having said that, they are hardly difficult to understand - if you can't understand the basic theories in sociology then you probably shouldn't be doing A-levels.
Other than the large amount which needs to be remembered, it isn't really that difficult. The concept of analysing and evaluating arguments and theories is a little bit difficult at first, but after some practice, it soon clicks.
Overall, I would recommend doing it. It is, for me at least, an interesting A-level which will make a change from the usual maths, english and science etc. Furthermore, it will undoubtedly develop your essay writing skills. There is the issue of "respectability", and as far as subjects go, it isn't generally perceived as being too "academically rigorous". Having said that, it doesn't find itself on LSE's or Cambridge's "soft list", and Oxbridge do in fact recommend it as a suitable A-level for some of their courses.