Two days ago my team was doing a global change in our style guide and we needed a visual regression tool to help us avoid unexpected issues. Unfortunately, PhantomCSS setup is complicated and we quickly got frustrated. That's why I crated Look-alike. It's convenient for ad hoc usage. (Note that it's not meant for cases where frequent, repetitive and multi-page tests are needed!)
Oh, and BTW - the whole thing is open source and available on github:
https://github.com/kdzwinel/Look-alike