Most touch phones (like, say, all iPhones) allow double tapping for certain actions. That's nice, but this feature also introduces an artificial 300ms delay for single taps! Now, that doesn't fare well with your otherwise über optimized UI.
90% of the time* , you just want to tap once (*I made that number up).
Fortunately, you can get rid of that sluggishness using a tiny, blessed lib. Meet Fastclick.js - Polyfill to remove click delays on browsers with touch UIs.
And oh, if you actually need that double tap for certain elements, you can fix it in your markup adding the "needsclick" class.
Hope you find it useful!