Since upgrading to Opera One, Opera windows with webpages loading (or at least some activity going on) steal focus repeatedly from the one I'm in. Like loading a webpage, reading in another window, and the one with the loading page pops up several times, making it impossible to do something else than watching this page load. Not even being in the process to mark something with my mouse or typing sth in a form prevents this.
This only works between different Opera windows, but not between Opera tabs and not with other apps like e.g. Office apps windows.
This is extremely annoying and by far compensates for any other cool feature Opera might have. I'm about days from swithing to firefox or chrome.
I just updated to version 100.0.4815.54, with the annoying behaviour still in place.