No, I haven't but I am planning on buying some books and software from them in future. I heard that the book on mental math isn't worth buying but I think I am gonna buy it anyway. There are still other resources to improve your mental maths skills like the video series by The Great Courses (
The Secrets of Mental Math | The Great Courses) which I got for free...
And MathTutorDVD should also have something related to mental math.
Glad2Teach which I also got for free...
And the YouTube channel tecmath.
Speaking of pilot aptitude resources, you may also give a look at Latest Pilot Jobs. They have a section dedicated to Compass Test and one dedicated to other pilot aptitude tests. You have to pay for a membership.