Far beyond any other piano instruments out there, and well worth the money (the Play version, which is scaled down for people who don't need so many controls and want to focus more on the music itself, costs €99 or about $130). Something I'll definitely get a lot of use out of, and already have; I threw out all my sampled pianos and such after getting this, saving disk space.
It's worth noting that there is one other physically-modelled piano software out there, 4Front's TruePianos. Having tried it before, I can say that Pianoteq is most certainly more realistic than it or any other piano I've used, sampled or otherwise (TruePianos, in particular, has an annoying tinny sound to the higher notes, which sounds very artificial).
Hats off to Modartt for this excellent piece of software.