That doesn't mean much, it's just a label. ST3 has been stable (and my main editor) for 2+ years now.

React was 0.15 until recently, and Node was adopted by major companies like Microsoft at 0.xx versions.

The way people number their versions does not mean anything (React is actually in v15 now). 0.xx has no meaning, except if the developer of the software explicitly indicates it's unfinished. Version numbers are entirely subjective by default.

I agree with you on the stability of Sublime Text, but the label beta has, on the opposite of version numbers, a consistent meaning: it's not finished.