I refuse to purchase any updated rule books (i.e 'annuals'), not because I want to exploit faulty rules, but because I feel that such updates should be provided free of charge, in PDF format.
Having said that, all I ever bring to battle are the BRB, armybook, and a copy of the current offical FAQ. If someone wants to enforce a ruling contained within the annuals, all they have to do is drag it out and show it to me. This rarely comes up, though, as 90% of the annual rulings are also covered in the FAQ.
Happy gaming....