Hi again!
Received my 2nd hand Sinsonido yesterday, here's my opinion...
The bass is
super light, which I find very nice. It's a bit lively, but you quickly get used to it. The assembly of the "fake" bouts are easy and straight forward.
The piezo-pickup has this weird stereo effect that I can't really seem to make friends with (read about it). It's just weird, totally late 60's to have the sound pan from left to right when you play up from the E-string to the G... weeeiiiirrddd..
The playability of my Sinsonido is extremely nice, low string height and flats. Just my taste. I'm actually impressed by it, amazing when you think of the price I've paid for it (300$ of the Bay).
The softbag is also nice, with seperate rooms for the bass, the bouts and accessories. Nice semi-thick padding. Thumbs up.
The only thing I can't get my head around is the tone control, which doesn't seem to work properly on my bass.

It does alter the sound, but not in the way a tone control should. Don't know if I can get this sorted out some way, we'll see. The sound of the bass is a TREBLE inferno, which is not directly my taste.