In the last few years, definitely. It's pretty reliable for the gist of most things, but you'll inevitably always get those CC errors where it completely fucks a sentence up and that results in the auto-translation being equally absymal.

EDIT: Since they allow creators to upload their own subtitles (and up until recently, iirc, allowed the option for creators to use community-submitted captions) I forgot to mention that videos (like the ones posted) where clearly the uploader has done some subtitling/captioning in their own language probably get translated even more accurately, since youtube's not relying on their own generated Chinese captions and then translating those to English.