This is just my experience.

I can play most songs in any key, but some keys are more comfortable to play certain phrases than others. For instance some minor/major double stops are easier and sound better in C, F, and G than in Bb, D# and B.

But for me I usually practice one version of the song in a female key, and one version in a male key.

When doing session work, I usually get the song, changes and key to be recorded before the session. Studio time is expensive, it is not good to waste money on a piano player not knowing the song he is hired to play. That said, we often do new arrangements and make up new phrases and motifs. But the key is usually allready established by the composer.

But who cares... if it sounds good, it is good. If you have to use the transpose button, do it. It doesn't make you a lesser player. I know great famous piano players who only knows ONE key! That doesn't stop them from making great music. I belive it was Irving Berlin (or other famous musical dude) how only knew how to play the black keys, and got a custom made piano that he could transpose by moving the hammers via some kind of contraption. We don't look down on guitarists from using a capo do we?

DocZ