The Confuser (the Nung Sornying one...) is really valuable as a revision aid, though as has been said above it contains a number of mistakes.
When studying for Flight Performance & Planning I thought I had it licked until I got a question on calculating an aerodrome pressure altitude wrong. I spent about 2 hours in the textbooks, searching PPRuNe etc working out why I had got it wrong, and ended up utterly confused. Next day my instructor and I spent an another hour looking at it from a variety of possible angles, and eventually agreed that the answer in the confuser was wrong.
This was all vindicated when the exact same question (though different numbers) came up in the exam, with the same possible right and wrong options. I chose my instructor's answer over the confuser and thankfully the CAA agreed.
Confusing indeed.