I remember in one of my performances in front of the school in middle school, I had to play the Fantasie-Impromptu. The grand piano had the dynamic range from about p to between mp and mf on a good piano, and the pedal half-worked. Even so, everyone seemed to like it, even the music teachers. It was fairly in tune. Now that I look back, it was not so bad.
My music teacher did tell me a story about when a famous pianist had to perform somewhere in Asia in a hotel. He got up to the stage, and realized the piano was slightly tilted (as in one of the legs was shorter). Around the hotel auditorium there were axes, I think for in case of fire somehow. He eventually got frustrated enough that he marched off the stage, seized and axe, and started hacking away at the longer leg. So, it became level and he started playing again.
Now, he was performing in a place where it was ridiculously humid, and in a D major piece, one of the vital keys (I think it was G) began to stick, and then more keys began to stick. Anyways, eventually the pianist got so frustrated that he marched off the stage, took the axe, and began chopping at the piano again. The audience at first thought it was because it was uneven, but soon they realized that he was not trying to level the piano, but that he was actually killing it! After he destroyed the horrible piano, he left the stage.
I don't think this is totally accurate, I'm just recalling it from memory. I think it happened a few years ago...