Opera released its first version of Opera 15 via the OperaNext channel. This release was supposed to be the first one with WebKit/Blink as its rendering engine instead of Opera's own Presto engine.
But, as some have feared, it has become clear that Opera developed a completely new browser with a new UI missing almost all the features that made Opera unique. The overwhelming majority of the >1000 commenters on the release post http://my.opera.com/desktopteam/blog/opera-next-15-0-released has big problems with the decisions.
Contrary to what many first thought, this is not a "tech preview" or "Alpha" release - it's the (feature complete) beta of Opera 15. Opera employees make that clear:
I (not in any way affiliated with Opera) want to find out more about whether people are really ditching Opera, and if so, why and to which browser they switch.