I have a Paulele bamboo uke. It has great sustain. The tone can be a little harsh, though. There are about five or six notes (starting a step or so above A 440) that have a loud, I'd even go with "screechy", sound. The uke doesn't respond much to the soprano ukulele mid-range frequencies---I think that's why some some higher pitches don't sound mellow. The low range does sound nice, though, especially with that sustain.
To get the sweetest sound from this uke, I simply strum it softly, like so...
One more observation: this uke is more muted by my body than any other uke I've played, like lots of its sound is begin generated by its back instead of its top. (The back is arched and un-braced; maybe it acts like a little bamboo speaker.) Minimizing contact between the Paulele's back and my chest helps get the best possible sound out of this uke.
If sound is your top priority, there are many better-sounding ukes available at the same price. Of course, if you're simply smitten with bamboo-uke style---like me---you'll love it.