When I first saw that other companies were producing d20 books, I realised instantly that soon there would be so many d20 books in the market, that it would be purely insane to buy everything. At that moment I decided to buy only WotCs books, and only some exceptional pearls from the other producers. Also I never buy the modules, because I like to make up my own scenarios. I didn't even buy the E&A or HBGB, because I can create characters without their help.