Gaming keyboard? No, you are better off buying a regular mechanical one. Most gaming keyboards come with features such as "backlit keyboard" or "gold plated USB" or "gaming profiles" or even "macro keys". These features are all pretty much useless. It's better to get a good quality mechanical keyboard, such as a Filco or Das or KBC. Personally if I was looking for a gaming keyboard, I'd go for a tenkeyless cherry MX red switch keyboard. Surprisingly one of the cheapest in this category is the CM QF Rapid. The KBC Poker is probably a bit more expensive, but they come in 60% and 40%, which I think is great for gaming because you can easily hit more keys. Ducky have also been making high quality "gaming" hardware, but they tend to focus on making quality hardware instead of adding novelty features (that said, there are models with backlighting). Gaming keypads are also getting popular, logitech and razer both sell them, I'm not sure how good the second generation razer keypads are, but the first gen are designed by belkin and are quite good. Personally I think keypad gaming is superior to keyboard, the layout is far superior, and you can control the arrows with your thumb easily - in games like DotA this means you can keep your mouse in a good position as you move around.
Gaming mouse? The main features on gaming mice are LEDs, profiles, on-the-fly DPI switching, high DPI and recently the "sniper button". Out of these, DPI switching and high DPI are the main things you would probably want. It depends what kind of gamer you are though. If you are a 1:1 CS player, then 6000 DPI won't do anything for you. RTS is probably the genre that benefits most from super high DPI. I usually play WC3 and SC2 on 4000+ DPI. Generally you can't find mice that are high quality and not labelled as gaming - other applications just don't need these features. I'd suggest a logitech mouse, they don't have excessive novelty features and LEDs, and they have good build quality. Razer would be the worst choice in this category - because they are tacky, and because they have poor build quality.
Gaming headset? Questionable. All you need is some good quality headphones with a mic. Most quality headphones don't come with mics obviously. If you don't play multiplayer, then ATH-M50s are fine. If you play multiplayer, then logitech probably makes the best headphones with mics. They have 5.1, 7.1 and wireless models too. Macro keys on a wireless headset are surprisingly useful, you can control your voice chat while away from the computer or when alt tabbed.
