Hi
I have used Airquiz for Air law, Aircraft technical and for Met. I have to say that it was fun to practice, but it is not really an accurate reflection of the type of q's that you will get on the exam papers. I had a big shock up call after using AirQuiz and then sitting the real air law paper as I don't think it really helped me.
If I was you i'd buy myself an up to date PPL Confuser (which helped me more), as this is much more realistic.