Scott,

this is a good thread.

I play mostly by ear/from memory. Although I can play in most easy keys (up to 4 sharps or flats), I find it easier to play in one or two keys. Lately, though, I find myself performing a lot more, and as I expand my repertoire to the music which is not all familiar, I find it comforting to have lead sheets to remind me of how it goes. Except for the most harmonically-challenging pieces, I do not use the chords on the lead sheet, but play my own harmonies, though I am talking about popular/not so popular music, not Debussy or Stravinsky.

Regrettably, I am not able to read music in real time, while playing the keyboard with the accompaniment going, though I could do it for clarinet (that was my musical training), decades ago.

Regards,
Alex