"Support for arrays with indexing starting at values different from 1. The array types are expected to be defined in packages, but now Julia provides an API for writing generic algorithms for arbitrary indexing schemes (#16260)."
Originally I thought total nightmare but now I'm not sure.
My guess is that most people who prefer zero-based feel strongly about it, and most people that like one-based don't care that much. If it really doesn't matter that much, I think Julia should've gone with zero. FFTs, Vandermonde matrices (least squares), polynomials, and pretty much anything where the array subscript relates to the mathematics is cleaner with zero-based arrays.
FWIW, as someone in the latter category (liking one-based indexing), I'd say you're partially correct: I'm not emotional attached to 1-based indexing the way some 0-based folks seem to be, but it's a practical nicety and one of the things I'm really glad Julia chose to do. Making 0-based the default would definitely reduce its appeal to me.
How do you multiply two matrices that use different indexing? Ignore the indexing differences?
It's also problematic when different libraries use different conventions (0-based vs 1-based). Can you use the output of one such library to feed another?
I think the varying indices are a great feature for porting old code over from other programming languages.