Do you have sticking or sluggish keys? Do wish your piano would play with a smoother, more consistent feel?
Your piano may need regulation.
Regulation is the adjustment of the mechanism (called "the action") responsible for the piano making a sound when you press a key.
The action mechanism is made up of an array of rods, levers and springs that must interact with each other at precise times throughout the process of depressing and releasing the key to allow for the hammers to hit the strings, the key to return to it's position and for the action to reset, ready for the next blow.
If any step in this process is out of time it will drastically affect the touch and feel of your piano, making it less responsive to your playing and even cause notes to not sound at all.
Having your piano regulated is great way to enhance the response you get from your piano.
After all, when your piano responds more accurately to your touch, the easier, better sounding and more enjoyable it is to play.