I began formal classical piano lessons at 4 and quickly became a proficient sight reader. As impressive as it may seem, I really suffered because my 'playing by ear' abilities were not encouraged or developed. It wasn't till I got into high school (playing rock and then jazz) that I finally appreciated how important 'playing by ear' is to your development as a complete musician. The printed music on a page is just a means to document the notes and provide basic tempo & volume indicators. On top of that, most commerically sold pop sheet music is arranged using bland chords (not the ones actually played on the record), and it's arrangement typically bland & totally out of context' to the song's original style. Many song's grooves, accents & phrasing just cannot be indicated on paper. Only by listening (with your ears), and memorizing can you make the song 'come to life'.
I perform my core repetoire by ear (memory), but rely on leadsheets (w/chords & lyrics) to serve as more of a road map for songs I'm not that familiar with. If I know the chord progression of a song, I can then easily improvise the melody & arrangerment by ear.
As a solo keyboard entertainer, I think it's important not to give the audience the impression you're reading from music. They need to feel that the music is coming from YOU. When politicians give speeches, they sound far less convincing when they look as if they're reading it from text. Eye contact & interaction with your audience is critcally important.
Scott
_________________________