I have never used an Ultranova, I do have 2 normal Nova's and a Supernova and use those a lot.

I am huge fan of the Kawai K4...I used it extensively on my Smackos - A Vampire Goes West album from earlier this year...there you can hear all the Kawai secrets it has this really fresh digital trammeled sound with lots of weird artefacts. Especially its filter is very "exotic" with a life of its own sometimes...I think it was originally a design fault that they changed in the later versions of the Kawai K4 or did I dream that?