These are pitfalls and usability concerns. Languages that make you actively work against the nature of the language are not good; programming languages should be making this stuff easy.

One-based indices stop being a "minor detail" as soon as you realize that out-of-bounds indexing doesn't fail, but returns nil. Time to re-examine all of your code. Combine this with the natural mathematical awkwardness of one-based indices and it can get really frustrating, really fast.

I had to do Lua for some game design stuff a few years ago, and these were the two things which stuck out at me almost immediately and bothered me during the entire ordeal. Maybe I've been spoiled by Python, Perl, Java, C++, C, and other languages, but it's deeply frustrating how wrong Lua is about this.