I've used Fish for many years, but frankly only for the great autocompletion. The streamlined theme/prompt system and oh-my-fish plugin management are quite nice too, but minor.
The rest of Fish features that are not bash-compatible are rather a pain, particularly environment variable management. In principle these features have a better design than in bash, but not that much better, and their use is infrequent enough to have to re-learn them every time. Unfortunately, they just end up being a minor inconvenience when you try to copy-paste setup instructions from docs, and I don't interact with these features otherwise.
The rest of Fish features that are not bash-compatible are rather a pain, particularly environment variable management. In principle these features have a better design than in bash, but not that much better, and their use is infrequent enough to have to re-learn them every time. Unfortunately, they just end up being a minor inconvenience when you try to copy-paste setup instructions from docs, and I don't interact with these features otherwise.