I love my Virus. So much, in fact, that I am contemplating buying a Snow. (Perhaps even the real deal, heavens portend!) I do have a few gripes with the PowerCore implementation, but they probably have as much to do with my host (Ableton Live) as with the synth itself.
One such gripe is the lack of being able to use it to route effects. ...This is a huge bummer, since the effects on the Virus are awesome. It's supposed to route effects, but for whatever reason, when I do what the manual says, I end up getting nasty crackling, as if latency is all screwed up and bouncing around.
Another gripe is the lack of patch-switching. I'm probably being stupid about this, but there doesn't seem to be any external control of patch selection, and thus, when I'm working on a track, I get four uses of the Virus (one per DSP), and that's it for the whole song. I would love to be able to switch patches mid-song, so that the limit becomes four uses at a time, rather than per song.
Lastly, the PowerCore itself seems to screw up my Mac (Dual G5), forcing me to disable sleep mode. If my Mac ever sleeps, it will ALWAYS crash (100% of the time, no exceptions) on recovery. ...and this only started happening once I put the PowerCore in.
If you know anything about these issues, please reply. I'd appreciate it. : )