i have Ivory and Pianoteq3.
Ivory does sounds more realistic when you play a single note but Pianoteq takes the cake when you put the pedal down and start to play phrases and chords.
What it lacks in realism of tone it definetly compensates in terms of inspiration and flow.
Its just fun to play.
And since there isnt anything like the definete pianosound i stopped worrying about it and just enjoy playing with a sound that resonates with me.

i used it in two of my clips
Northern Lites on Vimeo
The Mystery of Time on Vimeo

I am about to rerecord the second one with the new V-piano from Roland. It will be interesting to hear how that sounds.
Everything i heard from the V-piano sofar was pretty amazing.