Nope. I've tried it in the past, but my problem is that I am uncoordinated enough to do a tap while holding my phone in one hand. I need to use two hands for it. And I'm really not into gestures that require the use of two hands to execute.
My old HTC Touch Pro had a tweak called 'Flip to Lock'. Did exactly as it sounds. You flipped the phone in your hand and it locked. Flip it the other way and it unlocked. If Apple ever offers that, I'll be all over it.
EDIT: To be clear about the 'Flip to Lock' part, this was basically rotating the phone, not like literally tossing it in the air and flipping it then catching it. Ie., rotating it front to back.