The CPU useage issue seems a bit strange:
I've been using the demo as a VST - I can't get it to work at all as a standalone. It comes up, but it's so slow it's almost at crash point. I did manage to access the preferences menu and allocate my sound card to it this morning and get a couple of notes, but it won't do that now.
In VST mode I started to get the CPU useage problems, and I did a few experiments -
The first weird thing was that the useage went above 100%. I got over 900% at a couple of points.
The second weird thing was that although CPU useage relates to demand on the software, as you'd expect, it isn't entirely consistent. I managed to get an arpeggio running with several instances of the onboard effects - high demand things like echo and reverb, with no problems at all (and it sounded pretty good, BTW). But less CPU intensive things caused it to seize up. At one point just moving one of the filter sliders caused it to seize, though this worked perfectly at other times. I don't think that was connected with the number of active voices or anything else demanding, either.
But those percentages are what amazes me most.
BTW this is on a PC running Windows XP. The same PC runs other Arturia software including the MMV. The only Arturia software that's ever crashed is the MiniMg V, due to a problem that I resolved, so that doesn't count, and the MMV, which has only crashed once, when I tried something that you can't really do in software. So these CPU demands from the Jupiter seem odd in view of that.