Having just switched from 12 to 35 (as FreeBSD didn't support my new laptop's WiFi card, while Linux just barely does, but that's a different story) I actually mostly found it pretty good - at least after only 24 hours.
The thing I do find frustrating is that the command-line switch "opera -newwindow" doesn't open a new window like 12 did, but instead opens a new tab. Isn't that what "opera -newtab" is for?
The context is, if I want a new browser page I have a script (triggered from keyboard shortcut) that determines if there is already an Opera window on my current virtual desktop/workspace/whatever you want to call it. If there is, it calls newtab. If there isn't, it calls newwindow so I get a window visible. Instead now it just pops open a new tab on a window I can't see.
Is this supposed to happen? Or is some setting inherited from 12 interfering?