Hi
I'm a big user of Pianoteq on windows (desktop and laptop), but since a few years, I use my iPad for live concerts or street busking. I plug in a battery powered midi keyboard and a battery powered amp, and I'm ready.
The main benefit in using the iPad is weight and battery life (between 5 and 10 hours). The minus is storage room.
What I really enjoy with Pianoteq is the very light storage space footprint. If we wanted just a quarter of it's expressivity and sound quality, it would use up several Gigabytes of precious space.
For the moment, the offering in piano sounds on iOS isn't really wide. Ik-multimedia has a collection, but they sound very "soundfont'ish" (but less than most apps out there) and takes up quite a bit of space,
CMP grand piano has probably one of the nicest sound qualities out there, but it's around 1 Gb just for one piano sound, and it doesn't integrate very well with cubasis or other iOS DAW's
I often dream of having a pianoteq app, even if it's a cutdown version (I don't mind not having mic placement or effects other then reverb), that would give me a fantastic expressive piano sound, everywhere I go.
Until then, I'll continue busking with a lower quality piano, but continue recording my perf in midi, and then play it back on pianoteq when I get home.
Otherwise long live my favorite virtual instrument of all time