I can only comment on the demo version 1.03 but can report that the application does seem rather too CPU intensive.
I have found that I cannot even have one instance of the demo running - without any other VSTI's loaded in Cubase without crackling sound, glitching or hanging - CPU reports at maximum in Cubase.
I'm using a 3.0GHz P4 with 1GB RAM... and the system is optimised for audio work only!
I recently bought the Prophet V software and am very happy with how this performs in comparison.
I'd like to consider purchasing the Jupiter 8 V software but can't - at least not until there's a demo that I can 'demo' properly on my system.
... Hey guys (Arturia) do you think it's time to start a Beta testing programme for Jupiter 8 V?
Give me a call