I bought this pedal as a street musician needing some extra layers to my sound. I'd heard alot about the TC Helicon Harmony Singer range, and was excited to try it.
In terms of its harmony capabilities, it does a great job picking up the thirds, but has trouble sometimes getting the 5ths in tune. It's very important to be clear with the tonality you're playing on your instrument, and aim to get the chord or note played before the voice enters. Otherwise, you find yourself with a harmony that matches your earlier chord.
I'm pleased with the build; it's solid, though the knobs are quite high, so can quite easily be nudged slightly off where they want to be with your foot, if you're not watching exactly what you're doing. Same goes for the tone button, which I rarely use, as I find that the low cut and additional highs are a bit too much.
The reverbs are nice, subtle when used lightly, but you'll definitely get nicer plates from the desk.