One of my friends struck it rich at a really young age. He grew up fairly poor and suddenly came into a large amount of money, and he now spends it on infinite amounts of frivolous items. He actually owns a Slap Chop, George Foreman Grill and some ShamWoWs. He also buys many of the WoW peripherals. Not only did he buy the sparkle pony and about every pet that WoW has put out, he also buys the actual gaming items. He has the Tap Chat, the wireless WoW headset, even the Wrath keyboard and Blizzard MMO gaming mouse.
Personally, the only peripheral I've bought from Blizzard is an authenticator, which netted me the cute little core hound pet. However, the sense of security that my seven 80s won't be cleaned out while my account is used to spam trade for some gold selling site is the real reason I picked it up. I have a Logitech mouse and headset -- nothing super fancy, but they work just fine for me, and I paid less than one piece's worth of the Blizzard direct WoW paraphernalia. My girlfriend was going to buy me the WoW headset for my birthday, but I told her to save her money and get me a game card, as opposed to dropping over $100 on a headset. I told her if I were going to spend that kind of money on something for my computer, it would be to update pieces of the hardware, like a better graphics card or a new processor.
In the end, the decision whether or not to buy something comes down to the consumer, so I leave it to you, the WoW gaming public: Do you own any of the gaming peripherals for WoW? If so, do they actually help make you a better player? If you feel they actually aid your gaming experience, can you provide some examples or testimonials as to why?