This is just my opinion, and others might think the opposite. But I found the interface to be a little obtrusive. I certainly don't want this tool to pop up on any and every single applicable file that I'm hovering the mouse over.
I might very likely be missing something crucial here, but after my quick evaluation, I decided to pass this one, since I couldn't find any Preferences in order to set it up, so that it pops up less often (and only when I want it to). In such a case, where there IS a Preferences window somewhere in MacGizmo, please forgive me for missing it, but nevertheless, in that case I would suggest that the developer make it more clear how reach it.
Lots of people evaluate (software) products in a matter of seconds. And if you don't feel right at home from the start, you simply toss it away. So there's probably some room for improvements there.
I also found the window's graphic style a bit unconventional (which doesn't necessarily have to be all that wrong). Adding an option to set it to normal Finder style ui graphics would be great. Even adding a second, more clean and elegant graphic style would be prefereable. Something like the smallish windows in Aperture, where the windows are all different gradations of black (with transparency in them). This is meant as constructive criticism, as I'd love to see MacGizmo become a great app, since the main idea and concept are all great. And because of my very quick/limited/intolerant test evaluation, I'm not rating this down, as I might have missed some major qualities in that short time.
Good luck with further improvement!