[tstrimple]

When it's time to scale out your team and now you're trying to hire dozens of F# developers it starts to matter a lot more. You can throw a rock and hit a Java developer. I hate the language, but finding other people who can be productive in it is trivial compared to F#.

[pc86]

One of the common threads among companies I've worked at which I would consider "successful" is that they don't really classify developers based on what languages they've used before. If you're a good programmer you can become a net positive in almost any language in a few weeks to a few months, and productive within the first year. Some of the worst companies I've worked for were the type who would toss a resume in the trash because they had 1 year of experience in $LANG from a few years ago and not the "have used it for 3 of the last 3 years" they wanted.

[tstrimple]

I think it depends on what you mean by "successful". Surely multi-billion dollar financial organizations are by at least some definition successful. They are a complete shit show from a tech standpoint. They are so large they cannot effectively manage specialist developer staff outside of very narrow niches. Standardization when you've got thousands of developers across hundreds of products matters. Maybe some "successful" startup can make things work when they are small. But you'll find they start to standardize when they hit real scale.