They didn't drop semantic versioning (assuming you're talking about http://semver.org/), they're switching to it (see https://github.com/iojs/io.js/issues/28).

Node.js uses MINOR even = stable, odd = unstable (which is not semver) and is still in 0.x even though it's been used by giants in production all over the world for a couple years.

Honest question, do you have good luck with semantic versioning? I find it's pretty hit or miss on whether an X.Y.2 patch breaks functionality in the previous X.Y.1 build.