What did 3.4 give you that 2.7 already had? I have found bundled pip and asyncio useful, but I was using Py3 from 3.2, successfully. It didn't suddenly become usable at 3.4 for me.
I think what happened was that 3.2 was the first "real" release, when a lot of .0 bugs were shaken out; the 'u' prefix was added back around that time too, iirc.
This resulted in more developers actually porting their libraries, an effort that had been basically non-existent before. The result was that the 3.4 ecosystem actually got mature enough that Real Work could get done, and more end-users started moving.
IIRC 3.3 also had some big performance problems that were sorted in 3.4, but I cannot remember the details.
Personally, I did very little with 3.2 but actually built Real Stuff only with 3.4.
