i´m afraid it´s too late now, since i guess the boesendorfer ceus is no longer standing in the silent hall with all those microphones set up. if i´m wrong about that, please consider my thoughts.
i would have found it VERY interesting to listen to a live performance on this wonderful grand (i had the pleasure to work with it on a film project) classically recorded to tape via the microphones you used when sampling, and then have the midi data transferred from ceus to a pc or mac and then listen to the same performance played back with vienna imperial. this would give a very exact impression on how realistic vienna imperial reacts to live playing.
it is very hard to judge a sampled piano with just demos alone. demos sound good, that´s what they are made for. the crucial part of sampled pianos is how they react to your playing - and thus how they interact with your playing, for you don´t only play with your fingers, but also with your ears. i currently use garritan steinway (master keyboard is a yamaha yus-5 piano), and the sound is beautiful, but it does not do what i feel it should do when i play. this could be an issue of velocity curves, and the importance of this issue might be reduced with the mere number of sampled velocities.
so even if boesendorfer ceus has already been wrapped and delivered home, it still might be interesting to compare a live performance to a vienna imperial-playback using the midi data created with ceus.