> The worst that happens in reality is you have to wait a couple extra months for someone to release a new build of something you depend on (or heaven forbid, clone the source and build it yourself).

I think a lot of people reading this (who haven't used Scala, and are used to e.g Ruby and Python) may be confusing the implications of source incompatibility with binary incompatibility.

Python 2 -> Python 3 had (has) source incompatibility, which is a nightmare to deal with, especially because the changes are of a nature that make it difficult to port code automatically and reliability. (Contrast with Go pre-1.0 -> Go 1.0, which had source incompatibility but an automated code transformation tool which, unlike Python's, guaranteed correct code for all the breaking changes introduced).

The issues with Scala's incompatibility are largely along the lines of binary incompatibility, which affects package management (and build tools), but doesn't have as much of an impact on breaking compilation of existing source code, which are the nightmares that people are used to thinking about in the Ruby/Python world.

(Edit: updated in response to dbaupp's comment to clarify the differences between "2to3" and "go fix")