I think the new Blink-based browser is very promising. Of the major browsers, I love the combination of user interface, speed, and speed dial. I get the best readability of all browsers (with extension "Opera Font Rendering by thunder13"). I haven't embraced Aura yet (I'm a version 20 hold-out at present as version 21 seemed glitchy). But Aura may be a good thing too.
I believe the Chromium underpinnings provide more speed and security than Firefox can provide, and Opera seems just as responsive as Chrome with superior settings and settings menus and possibly better privacy (though I tweak Chrome for better security too). In short, I think the new Opera is very nearly a KILLER BROWSER, fully deserving of big market share gains, EXCEPT... it needs to add full bookmark support and sync. Sync could at first be just between Windows desktop installations. Later, of course, it would be nice to expand sync to cross-platform. I can't recommend Opera to any friends in its current state. It's not capable of being one's only browser.
When it has bookmark support and sync (at least among Windows desktop installations), I believe it can enjoy significant market share growth. Would that cause friction with Google? Perhaps... but that's a GOOD problem to have, right?
I suspect I'm a mainstream browser user. I've been curious about Opera through the years and have downloaded and tried it from time to time and then headed back to Firefox as it's flexible and solid and reliable. I love the competition that has developed in browsers though and the resulting enhancements in speed and refined interface. I keep looking because I'm hopeful that I'll find the perfect browser. The new Opera is close. I hope it gets there. If it doesn't add bookmarks and sync though, I'll finally give up and go back to Chrome or Firefox.