I began work on League Mono at the end of 2016, and had the bulk of it in a usable form in March of this year. Why? I had been looking through the League catalog and realized that it was missing a monospace family. There's no shortage of great, free monospace typefaces in the world (links below). That realization allowed me to play around and not worry about the success or failure of a new open source contribution.
When anyone asks me how they should get started with type design, it's hard for me to answer without in return asking them a dozen or so questions. But I'll make a blanket statement here: if you know you want to make a typeface from scratch (as opposed to vectorizing handwriting/script) on your own (without going to a workshop, or school) but aren't sure what style to try, go monospace. The constraints involved (fixed width, no kerning) means you'll have a more focused, productive experience. And with that I'm going to show few other of my favorite fixed-width fonts that I've used in previous work, alongside the new League Mono.
League Mono actually does okay for simple programming, which is not the application I had in mind while working on it. I prefer to code in text editors with a bright font on a dark background, so the light weight of League Mono is particularly handy (some of the others included here and elsewhere don't have a light weight, which is another reason I really wanted to make my own). That said, Source Code Pro is absolutely perfect for this use. I also love Courier Prime Code for this, too. Take a look at the screenshots all taken in TextWrangler at the same cropped part of the window (big line height differences).
Each of these (and hopefully League Mono) works well in their own way. I've been setting more and more type in monospace fonts lately, and all six here are free, and even though some of these are not new, they might be the first time you're seeing them: Fira Mono, Source Code Pro, Courier Prime Code, Droid Sans Mono, PT Mono, and League Mono.
I look forward to seeing League Mono out in the world. Enjoy!