Several different conversations going on here...

I am a pretty good at transposing. It's something I work on just about every day. I go through the blues, rhythm changes, ii V I, all sorts of licks, scales, Hannon exercises and tunes and play them in all 12 keys.

But yeah, sometimes I still use the transpose function on my keyboard, but I try not to. The chord voicing can sound too high or muddy when using the transpose button. Sometimes I forget to turn it off when going to the next song, now that's embarrassing! And as Tony said, when playing with other musicians, it can be difficult to communicate about the chords and notes of the song when your both playing in different keys.

So I just try to use it in "emergency situations".

When I have time I try to learn the tune in the key it's going to be played in. Every once in awhile, opportunities come up where I'm asked to play on an acoustic piano. Those of course don't have transpose buttons, so I want to ready for those situations and not make excuses like " I can only play on my keyboard" That's silly!

As far as playing from charts vs. memory, I also do a lot of both. Ideally we should have everything memorized. If I have enough advanced notice about a gig, I do put in a lot of prep time trying to memorize or at least being able to play without staring at the page. But there are only so many hours in day to prepare. Sometimes I get last minuet calls to back up singers with no time to prep. I use charts and the transpose function quite a bit in those situations. Anything to get the job done well!