Whenever I see an app get three 5-star reviews in quick succession from people who have only just joined MacUpdate and who have only reviewed the app in question, and who only use a one-liner basically saying "this app is great", I get interested. Is the app really this good? I work a lot with icons so I had to download it to see for myself.
Ok, if you want a quick way to assign a custom icon to a single, or multiple folders at once, and you're happy with the bundled icons, then this app does that. The interface isn't particularly elegant, but it's functional & gets the job done. Drag the folder(s) you want to change onto the app, double-click the icon you want to use, job done. Many of the bundled icons weren't to my liking, but that's purely down to individual taste. (I'm assuming they're royalty free images from around the web as I've seen some of them before elsewhere).
My major problem is that the app allowed me to assign a custom icon just 3 times before telling me my trial was over!! Not really sufficient time to see how useful it would really be, how stable it is, what features it might have, etc. The help also seems to be sadly lacking, so I wasn't able to explore how the 'custom' categories work. There is a short video (no audio) on the website, but it only covers the basic function and not how to add your own custom icons. I did try dragging a few png images into the custom section, but for some reason FIC didn't arrange them at all and they disappeared when I quit the app and relaunched it (maybe that's another trial limitation?). Also there doesn't appear to be any way to edit/modify the icons, which many of the icon-changing apps allow you to do. I did hope that was what the 'customize' icon on the toolbar was for, but that just lets you customize the toolbar itself.
So, from what I can tell this app does one thing, and appears to do it ok. Beyond that I can't say owing to the somewhat 'severe' trial limitation.