Things seem a little one sided here, and I thought some praise is due where it is deserved.
The only reason I ever used any browser other than Opera was because it became too slow to use with Facebook. Here's why this happened:
Facebok began as a bunch of crappy php scripts and some javascript. Since they were to experience expoential growth forever, performance problems both on the servers and on the brower side began to suffer. To add to this there was a large influx of people that left Google and went to Facebook and with them they took the idea "hey, do it in javascript with ajax - way way better and hey, you know, the Google V8 Javascript engine is 10X faster so we can do ALL OF THE STUFF now. And right way non V8 browsers began to get slow. This was around 2009 when Facebook intriduced "auto page refresh" to compete with Twitter who had just added it. Things wend bad from that point and in only two years it was easy to get a browser that ends up in a state spending more time updating itself than letting the user actually do anything. But, there was Chrome, and if you switched to that, Facebook was fine. For a while. Now it's as bad as Opera was in 2010. FB is gonna have to do something, you shouldn't need a 6 core CPU and an 884 core GPU to run the moral equivalent of Usenet with pictures. Ahem.
Anyway, the point it, since I downloaded Opera 17 about a week and and got over the freakout of ALL OF THE FEATURES THAT MAKE IT OPERA ARE GONE I came to realize...
...i haven't needed to run Chrome in a week. Ok, that's pretty impressive. Opera was starting to fall behind even Mozilla, with no hope of matching Chrome's performance (but who cares, it crashes all the f'ing time and doesn't work with forms, it'd rather have slow but works than fast bu doesn't!) but has now leapfrogged past Mozilla and replaced the need to ever use Chrome again. Ok, that's a big deal and deserves recognition.
The other thing is the aesthetics. I will admit to the xmas tree effect in my own copy of 12 and the new one is so minimalist it's actually refreshing. I can understand why Opera wants to add things slowly are carefully. That's commendable. Also the look and feel of the browser and the better web pages has improved dramatically in the last 8-14 months, to be sure a lot of this was driven by phone, but none the less the progress is staggering and I'm impressed.
It's a tough decision but I think once we get past the short term pain there's long term gain to be had.
So... constructive criticism. I realize not there's tons of bulky Opera 12 features that aren't in 17 and I don't miss and I'm glad I'm not paying the storage and computational overhead for them: sync, unite, mail, irc, torrent... all that Swiss Army Knife stuff. So I'm glad that's gone and it would be nice that if they came back they came back as some sort of loadable (and unloadable!) module. I do want dragonfly but I never want it all the time and wouldn't even mind firing up a different version of Opera to get it. I can live with that even.
But, despite the long list of things I'd like to have from 12 be new features in 15 there's really only one I can't actually live without and that's the ability to edit forms properly which currently doesn't work in Opera 17 or Chrome 30. The problem is if you half fill out a form then go to another page then go back - everything you typed in is gone now, and without this, you can't use a browser to edit some things, that it it, new Opera breaks some apps that work in old Opera.
Opera used to be the only browser that got this right (Mozilla fixed this and works now too) and got sold into a lot of installations that relied on accurate editing where only Opera worked. They can't upgrade, they have to switch to Mozilla now, or stay with Opera 12.
As a programmer, I don't even care all the -o- stuff is gone and the -webkit stuff is different, I can work around that, but I can't work around a browser that had a fundamental and essential property suddenly go away with no warning. So, if it were me, I'd fix this first. Because if this isn't fixed, than it does't really matter if anything else gets fixed because it can't be used.
It's taken 15 years too long to convince business and government to use http instead of paper and to suddenly go from 1 to 2 to 1 programs that can used for this is not progress though and would like to hear this is something that is fairly high up in the queue of things to do next.
Speaking of hearing things, is there some official channel to find out what future directions are in the short, medium and long terms? They only way I can see on the Opera site per se is the job ads which to indicate some direction but not as to the specifics of the future of the browser. Perhaps I missed it? Perhaps if one doesn't exist something like that could be created?