The configuration of the Eventide H3000 Ultra Harmonizer isn't the easiest to follow, and since it is a unique effect, it takes a little while to understand and be able to use everything on this unit. There aren't that many parameters, but the lay out is sometimes hard to follow since it is one of the first analog harmonizers out there. The possibilities are pretty varied when it comes to this unit, but isn't the easiest unit to navigate on.
The sound quality of the Eventide H3000 Ultra Harmonizer is pretty good considering how old this unit is. It can definitely be useful in the studio if you want to figure out or add some harmony parts to your vocals or any other instruments you might want to add to. I mostly have used the Eventide H3000 Ultra Harmonizer for vocals, but have also tried it on guitar and keyboards, with some pretty interesting and cool results.
I've been using the Eventide H3000 Ultra Harmonizer for about five years and it is definitely an interesting piece of gear to say the least. When it comes to harmonies, I would rather actually sing them myself than let a machine do them for me, but this can provide you with some awesome sounding effects and definitely has interesting creative capabilities to it. The price isn't that cheap if you can find one used, but I wouldn't really recommend buying one of these unless you are a professional studio anyway because it isn't worth it this day and age. The Eventide H3000 Ultra Harmonizer is definitely worthy of a try though.