Coffee added really nice and productive language features to what at the time still was a very primitive and simplistic Javascript. It also offered a different syntax to existing and new features.
The first part was great and deserves credit for pushing the language to evolve. The second part made it a terrible dev experience. My experience was identical to the gp: writing it was fast and intuitive, but reading it was much, much worse. Not just reading other people's code, but even my own: my ability to understand my own code degraded not in weeks or months, but mere days. It was so bad, the overall result was a net negative and I quickly stopped using it. I say this as someone who has enjoyed writing code in over a dozen languages, from assembly all the way to Haskell.
The first part was great and deserves credit for pushing the language to evolve. The second part made it a terrible dev experience. My experience was identical to the gp: writing it was fast and intuitive, but reading it was much, much worse. Not just reading other people's code, but even my own: my ability to understand my own code degraded not in weeks or months, but mere days. It was so bad, the overall result was a net negative and I quickly stopped using it. I say this as someone who has enjoyed writing code in over a dozen languages, from assembly all the way to Haskell.