I've got an all-black Kala archtop...regretting that now because we need more sunburst in the ukulele world. But anyway, unplugged, it's deader than a doornail. The one I have wouldn't know what sustain is, if sustain punched it in a bar brawl.
That's the bad. The good is that it's ment to be used plugged in anyway, so what does it matter? The electronics are good enough for my amps anyway, and you can make it sound like whatever you want.
And it the neck feels great to play on, as comfy as a tenor can be. I just wish it was sunburst. Ah well.