In general chords just sound horrible and the effect is really only noticeable round the 10th to 14th frets. Some people disregard it as a one-trick pony, and in a way I agree.
I've built a few Octave Up pedals over the years, some I've kept, some I've sold.
Honestly I can't even remember all of the pedals I've made & parted with.
Pretty sure I built a green-ringer once upon a time.
Don't remember selling it or destroying it, but it isn't in the arsenal any longer.
Anyway, my point is, I like the effect enough to keep building variants, but my favourite is the cheese wedge of the Jim Dunlop - OC1 Octavio.
The Octave Up is clear and distinct for about 90% of the Fuzz range, then you hit this tipping point where the Fuzz is really intense and the octave becomes really dirty. It is a pretty loud pedal and has a tendency to clip the input of any buffered bypass effects in the chain.
I've mostly played it with a regular 6 string and it has been an enjoyably noisy affair, but recently things have taken a turn to the lower end of the range as I have acquired a Bass VI.
I used to think that it would only really suit the 12th fret region on a regular guitar, so never bothered with a bass instrument. I was wrong and I was missing out. The Bass VI produces the octave effect very clearly when playing reasonably calmly, but start going a bit silly and every note distorst in a way that evokes an auditory image of a torn speaker.
Try running it with a nearly exhausted battery. It does gets into synthesizer territory.
Hmm... I think I might need to build a flat battery simulator soon.....