I came in contact with the language during my studies (one of my profs worked on it), found it interesting, but haven't really had a chance to apply it to anything I've done professionally since. It's a very neat language though, and if I got to do anything in the embedded field.
I notice that there is now an open source compiler, which is great. The only implementation I was aware of so far was closed source.
https://en.wikipedia.org/wiki/Esterel
(if you'd like to throw a link in your comment, would be happy to delete this one)