Don't use code that only runs on Linux. Swapping one monoculture for another isn't an improvement.

If you're writing stuff for server use, and it's not being tested on a few Unix implementations, you're quickly working towards being a single-platform monoculture. This limits your options if a platform falls out of favor or is EOL'ed by a vendor.

It's a good thing that OS X is so popular among the hacker set - if it wasn't, I think the quagmire would be even deeper.