Left handed people think with their left hands, so playing a"normal" piano means leading with the hand you don't use so well. Nowadays there are left handed scissors, left handed cups etc, so why not left handed pianos? A lot of left handers learn to adapt to a right handed world so well they don't even realize where their natural facilities lie. One test is to copy script with both hands separately. If there's little difference, you're either naturally ambidextrous, or a left hander who's learned to use your right. Please follow this lovely link to Geza Lozo's site, and pass it on to left handers everywhere. You never know who it might help!
He sells scores too, classical and even pop, which use the same notes, but reversed so they're easier to follow. Follow this link for a video of Loso's son playing a left handed piano.