It IMMENSE... you'll find it useful in all your other subjects because it trains you in a certain way of thinking. If you're anythign liek me you'll hate it at first but grow to love it.
It's a very simple and quite useful course. But the subject content is quite/very little, and really it is only applying it to newspaper articles that is tricky. The exam though is actually a little harder (although I had very little practice before the exam - and came out with a B at AS): making up your own arguments, analysing more advanced texts etc.
I wasn't too fond of it - it's packaged as some "amazing AS that develops your mind", although I personally thought that you weren't really allowed to think; I had the feeling that if you don't put down the sorts of things the examiners want, you won't get a good mark.
As I say, it's an extra AS - and it's easy to get an A or B if you work moderately well at it all year.
In my sixthform it was an "extra" that no one, not even the teachers really cared about. It was also the first year they did it so i dont really think they knew what to expect.
I didnt see the point of it really and some unis dont except it.
^ What you (presumably) meant to say was "some unis don't accept it" (which is true); but what it actually said was "some unis don't except [they actually count] it" - which is also true.