I have one.
It's not bad.
The octave fuzz isn't that amazing IMO.
You can get some interesting tones out of it... if you want your bass to sound like a saxophone.
IMO it's good for off-the-wall bass solos, but not good for backing up distorted guitars.
But it sucks out the low end.
That why I rather use a Hairy Balls now because that keeps an awesome deep low end while shredding in the lowest register.
I'm experimenting with the HB gate control to make it more suitable for fast heavy metal riffs.
The FZ-5 is not a bad fuzz pedal for your first step into the world of fuzz, but there are tons of better alternatives for fuzz pedal.