To Your original Question: now always ON.
Previously I had definitely performance problems and more latency with my Kontakt instruments, but since K4.2 there is a zero-latency option, which You can use for the cost of higher CPU load . (I think the Galaxies 1.2 use this as default setting).

For the Concert Grand, at its lowest setting without being turned off.

I always turn it off. I think that reverb put a 'mask' on how I play. I turn it off.

I prefer reverb off with dual piano sound in my Kawai CA93. With high volume it sounds very well.

Reverb is artifitial and, as somebody has said, masks your playing.

Always off for me. It's the first thing I do after turning on my FP-7F - my fingers have better muscle memory for that than for actual playing

I don't particularly like the sound of the reverb. It sounds artificial to me in headphones, and even if it sounded more natural I think it would still sound weird when playing through speakers because it wouldn't sound like the natural acoustics of the room.

But that's not the primary reason for me. I prefer to hear a clearer, cleaner sound when practicing.

Love my reverb. I use it all the time with my CP33. Love reverb so much, I pick up my outboard effects processor tomorrow. A TC Electronic M300.

It depends on the situation whether or not I use reverb. I mostly play in a band setting so I usually turn the reverb off as it makes the piano sound too muddy and indistinguishable in the mix.

However, if I am playing solo piano, or a song has some type of single note octave piano lead I will use reverb at a medium setting on whatever keyboard I use. Actually, in the latter situation I will probably turn the reverb to max and add some delay, almost like a guitarist would during a solo.

On 'room' all the time on my RD700NX

Until yesterday, reverb off forever. I like dry pianos because, to my ears, they lose their little realism as soon as reverb is switched on. But often, dry means thin, too. Then, last night I set reverb to low depht and duration and I found it less unpleasant. Anyway, I don`t like it very much, for me sounds too "electronic", especially with headphones. Hope I'd be able to manage it to get a fatter sound.

P.S.:...and back to perception, I'm not too old (wich has a large influence in how high frequencies are perceived), and my ear is very sensitive (more than average).

Always off when generating sound on my old Technics - 90's model; reverb unnatural and unconvincing.

Always on when using Ivory II to generate sound (played back through the Technics 6 speaker 2 x 50w config). Sympathetic resonance, Damper Resonance and Ambience all pleasant and sound natural.

I sometimes wonder if DP technology has really moved on, but when I think about it from this perspective it's clear to me that it has.