Paia's are pretty cool and there is a strong community of modders out there, but what's up with the wack voltage?
Has anyone ever used Tassman? Its my favorite soft synth out there. Totally based on modular synthesis. Its somewhat similar to Reaktor, but in my opinion it feels a lot more like using a modular and has much better sounding high frequencies.
Its a great learning tool if you're thinking about getting into modulars.
The downside? It sucks the life out of your cpu.
http://www.applied-acoustics.com/tassman.htm