support for a shell you don't use is a negative? why? I don't personally use it, but I don't mind if other people do -- what's the problem here? just curious.

Fish shell detracts from people learning (and maintaining) to use POSIX compliant shell scripting. Professionals should be ready at a moments notice to use bash, zsh, and ksh. Also good to be familiar with a csh, (I would accept tcsh). Learn to use the tools of the trade, not toys.