I use fish but only interactively. For scripts I still use bash. The amount of fish-specific syntax I use interactively (and, string interpolation etc.) is so small, it doesn't really bother me.

Addendum: I did write my entire prompt (which is 81 lines right now) in fish (my rationale was "maybe it's better performance-wise"), which was hell and I hated it but that's the only piece of fish code I've ever written.