Opera, which was my favorite browser since 2003, has recently switched to the new rendering engine, Blink. Blink is a fork of Apple's popular WebKit engine; there are a number of browsers which use it as well. Opera claimed that they will work with Google to improve and extend Blink, and even since they went in that direction, Opera looks and acts more and more like Google Chrome. Personally for me, the user experience does not have anything in common with the classic Opera browser any more.
If you miss the classic Opera browser, there's good news for you: you can easily get almost any previous version of the classic Opera installer for free.