A small nitpick: the piano is actually a string instrument, not percussion.
Though it can be used as both, it hard to argue that when Jerry Lee Lewis was pumping it it was a rhythm/percussion instrument, in most Latin music it tends to be more percussive then melodic.
But in the context we are using it here, it's not either, it's a keyboard. In a late romantic/modern orchestra, the piano is in fact part of the 'keyboards' section along with a celesta, while it would not be any part of a classical or early romantic orchestra. It is placed behind the violins, between the harp and the timpani (on the house/conductors left, or stage right if you think in those terms) in a standard set up. Thus making it somewhat of a bridge between the stings and the percussion. But while it can be played as both, it has a keyboard, and as such is a keyboard, not a sting or percussion instrument in your stage plot. For something like a piano concerto you have to drag it out front. And trying to move something like a concert grand w/o putting it out of tune is all but impossible, so it would be set in the front and the concerto tends to be done first, so it can be moved off later. You'd think something that huge and that heavy would be all but impossible to mess up the tuning on, but you'd be wrong, if you even as much as look at them cross-eyed they will betray you. Piano's have been hatin' on stagehands since the 1750's.*
They be hatin' on piano tuners also, I've seen tuners called back to re-tune them suckers three and four times until they are all but reduced to tears trying to get it - not close, but absolutely perfect in an environment that is constantly changing. I can pretty much put a piano out of tune - particularly if it's a black one - just by turning on the stage lights and leaving them on for half-an-hour. Any more I have a white sheet that I toss over the piano if we have to focus the lights after the piano has been tuned.
Taking up the piano will however keep you out of the marching band. Reason enough for several people I know to have taken it up as opposed to some other instrument.
* - I work for the symphony (both SF and SR) because you don't live by rock alone, and because I did it through college (and mostly because I own a tux) where we referred to our two stage pianos (one a concert grand Steinway the other a concert grand Baldwin) as the 747 and the DC-10 respectively.
