I'd consider the reception of a software product update to merely be "positive" if there was generally praise, basically no negativity at all, and people expressing that they are now significantly better off.
"Very positive" would involve no negativity, and complete and total jubilation from users. This is extremely rare.
A lot of people are not happy about Australis, and justifiably so. While Firefox has been imitating Chrome the past few years, Australis sealed the deal and made them nearly identical in the most critical ways.
The only mitigating factor is that there really isn't a viable alternative to either Chrome or Firefox these days. Opera has basically become Chrome, and Safari obviously has very similar roots. IE is engaging in the same imitation of Chrome. Both IE and Safari suffer from a lack of portability, too.
Many Firefox users are extremely disappointed with Australis, but they have no recourse. Switching browsers isn't really an option. And we wouldn't be in this position had Mozilla listened to all of the past feedback they've been given, so giving more feedback is probably a pointless exercise. So they suck it up, as best they can.
Australis was a debacle, at best. I think you're deceiving yourself, and people not familiar with the situation, to suggest otherwise.