I found the red one for sale for $100, and I heard that the blue and Hendrix will be the same price. That's pretty awesome. Jeorge Tripps deserves the hype around him, these things are awesome.
They've only just been annouced, so nobody can say for sure, but logic would dictate that they sound the same as their big cousins, although exceptions may be made when using a power source instead of a battery.
I wonder what the regular SI one is based off - perhaps the buffered BC108 Classic fuzz thingy?
There's so much space inside a FF that I wouldn't doubt you could fit it in 1/4 of the size. Maybe use a power supply with the output that has the slightly lower voltage option