I use Firefox since it was Phoenix, back on my Windows 2003 and except there was time when it was noticeable slow so I was forced to use Chrome/IE I hardly can find things to complain about regarding changes.
I see other people complain a lot, which makes me think I'm missing some big part/have some unusual usage for Firefox. Any hints what I may be missing/doing strange way?
Generally speaking, FireFox still retains most of the same features, it's just harder to configure it to be well-behaved (tab bar on the side was a native Firefox preference originally- now it is a real learning experience to set up). There is also a lot of stuff bundled and enabled with Firefox by default that ought not be included at all (WTF is a "pocket"?).