hairystuff :
faster response times, no key ghosting, backlighting, additional function keys, higher resolution cursor tracking all theses things can make gaming more fun.
The difference in polling between what are common peripherals and what are "gaming" are more often than not the same these days. In fact, though it would lead to a very much more complex discussion, some pro counterstrike players for instance prefer a polling of about half what is the "gaming standard" 1k hz for reasons that has to do with how the update jogs and how 1k hz can induce very slight jitter).
Most "gaming" keyboards do not have any increased anti-ghosting properties. Any of the standard gaming tagged Logitech G series keyboards for instance have standard anti-ghosting as any other 6kro keyboard. The only one short of certain mechanical keyboards that can make the anti-ghosting claim effectively is the Sidewinder X4 from Microsoft which is ugly, but does in fact have sufficient anti-ghosting to mention it as a feature.
Backlighting I've never thought added anything to gaming since most people who are gaming on their computers are also touch typists of varying ability, but it can look cool I guess.
If by higher-resolution cursor tracking you're referring to DPI, increasing DPI above the comfort threshold of 99% of computer-users isn't a gaming secret. It's just marketing. Most people are comfortable with their mice between 1800-2300 DPI for normal use, and some FPS players like having their DPI able to go extremely low if they are swipe-players. You won't find anyone using 5600 or 6400 or any of the gimmick dpi's though. They're just too fast. The thought of forum posters on other sites to increase the DPI to the max and then turn down sensitivity in windows to get "high resolution tracking" is in fact doubly counterproductive. Increasing the DPI while reducing the sens only creates more math for the computer to do, and introduces negative acceleration (which is a product of altering windows mouse sens).
So, I wrote all of that to highlight some points. OP, the vast majority of what makes a "gaming" mouse and keyboard as such, is just marketing. In the end, get what you feel comfortable with. Mouse and Keyboard are user-interface devices, and their shape and functionality play a very important role in how well you will perform with them. Don't get wrapped up too deeply in marketing hype, because a lot of it is as relevant as the crazy borderline-lies you see surrounding monitor advertising.
P.S.- If you see a pro gamer using something boring like a Microsoft Intellimouse, it's not necessarily because it has secret good JuJu powers. Most pro gamers try to stick with peripherals that are a familiar shape as what got them to where they are in the first place. I don't have the thread anymore but there was an interesting discussion on Overclockers a long time ago where some CS Pros were posting exactly why it was they used the mice and keyboards that they do. It was simply because those were the models of mouse and KB that they had grown up playing with.