OK, I almost wrote a negative review about this effect. Sorry, my mistake. To make a long story short: it was not the Helicon, but wrong settings on the amplifier.
If there is one thing I don't like about this effect pedal, it's the fact that there are so many options and buttons, that it takes a long time to find out how everything works (and how it doesn't work). And you will be down on the floor a lot of times, adjusting the settings.
The looper is not interesting (too short and hard to handle). The overall sound quality depends a lot on good XLR cables and a decent amplifier. (And good settings).
But after a while, you will find out it's fun.
Free advice:
1. You can find a lot of extra settings on the webpage of Helicon. +500 settings. And it's worth to upgrade this effect on the same webpage.
2. Beware for too much voice compression; it can cause feedback or strange guitar sounds if you use harmony vocals if the mike picks up the guitar sound.
3. Very important is the gain control for a decent sound. Too strong results in feedback and rumble, too weak results in strange harmony vocals.
4. Again, if possible, use a XLR cable for the guitar input on your amplifier, it will make a big difference.