This review is written by a synth user for synth users.
I bought Thunderstorm for my two synths: Odyssey and Model D. It works well for both. Sound-wise there's nothing to complain. It does its job of being a flanger pedal.
From a synth user (sound designer) perspective, this pedal is not very versatile. It's not bad as many other flanger pedals are even more limited. I would say that it allows for different sonic palettes but for real experimental users it may lack more extreme settings.
To summarize, it's a good flanger pedal for synths if you just need a flanger and you don't want to go into any extremes. Leads, pads, basses - it will do. Crazy, strange, aggressive sounds - look for something else.