I haven't used it, but have read enough to say it "works" if you very carefully qualify "working." Type and size of cracks is the first question. Color is an issue. Reviews of it are very mixed and it's all based on expectations. It's not as magical as the youtube video makes it seem, but nothing ever is. They have three different products too so be sure if you try it you get the right one for your job.
There are dozens of reviews on Amazon and a few elsewhere. They are very useful not just for the score but the detail of what the reviewer used it for, those who had success and those who had failure.
I know two people personally who have used it. The first loved it and recommended it to the second who hated it.