Ranked in these QuestionsQuestion Ranking
Pro Compatible with Chrome extensions
Since Opera is built on WebKit, the same engine Chrome (among other browsers) is built on, it was possible for Opera developers to allow Chrome extensions to run in their browser.
Pro Strong HTML5 feature support
Opera scores highly on HTML5 feature support.
Pro Opera turbo
Opera has a functionality called Turbo which increases browsers speed and reduces data consumption considerably by compressing the data that's found in a web page.
Opera is full of user controlled settings. Everything can be imported and exported even RSS feeds. It can be skinned in a variety of different themes or it can be extended through the use of a large number of plugins available.
Pro Video pop-out feature.
You can pop-out any video and it will stay on top while you are surfing on other tabs.
Pro AdBlocker onboard
It's possible to add own filter lists. The internal adblocker is faster than any external.
Pro VPN onboard
Free and fast VPN onboard, includes Germany, Canada, USA, Netherlands, Singapore.
Pro Battery saving mode
Pro Free and open source
Con Less extensions
While Opera is currently available gratis (without monetary charge), it is currently not libre (meaning that it does not allow users to view the source code used to create, to modify that code, or to redistribute modifications) and is therefor neither free nor open-source software.
Con Some search engines + shortkeys are predefined and not editable
Con Original version using Presto engine is dead
Current version is built on WebKit/Blink, which means it shares cons of Chromium: high RAM usage, lack of customizability.