One thing to stress. This is NOT a multi effects unit, e.g. an effect may contain reverb as a parameter, as distinct to reverb as an effect, but you can only use one effect at a time. Zoom's terminology indicates that a program is really just an effect with preferred parameters set.
Its intended use is for enhancing sounds in a studio, some presets being designed for gating drums, enhancing vocals, getting the best out of a piano, etc.
There are comments on the lack of distortion effects. I found, using a strat copy which doesn't have overly high powered pickups, the level for a patch would need to be no higher than 50 (out of 99) to maintain a clean sound. Higher levels actually give a nice overdrive as opposed to fuzz/distortion sound.
The harmoniser is not intelligent, the robot is a gimmick, the other sounds are actually quite nice, quite usable.
This thing, for one effect at a time is easy to use and sounds much better than the 505ii or many other effects units.
Similar to another reviewer, I find that it doesn't always immediately fire up when switched on, unless I tap it against my palm. Maybe it has something to do with dirty battery contacts. It is not a floor pedal, and with normal treatment should be sufficiently durable.
At first I thought I paid too much, but compared to a Zoom 1010, 505ii, Korg A5, I think this sounds nicer and is easier to get it to do what I want. I would replace it, but wouldn't expect to see another, altho I would preferably pay about half as much!