Personally, after almost a year, I haven't adapted and I don't think I ever will. O12 is still my primary browser, although I always have the latest Opera Developer installed which I sometimes use for Facebook and Gmail (unusable in O12).
I still miss the standard menu bar, the bookmarks menu, the download dialog and manager, the MDI common close tab button, the tab behavior "click on tab to minimize" which allows one to go back to the last tab, etc.
I keep using the latest Opera as a secondary browser out of a mix of nostalgia and self-deception, but it's not really even my second favorite browser, I prefer Firefox. Although I also must say I prefer the new Opera to Chrome (for things like native mouse gestures). My ranking would be something like O12 > Firefox > IE tied with new Opera > Chrome.
BTW, so you see I'm not all negative, the feature that appeared very recently in the new Opera by which the tab preview when hovering over a tab is big and readable instead of just a thumbnail, is really cool and useful. But sadly it's the only advantage I can find in the new Opera, and it is far from outweighing all the missing things.
I'm also waiting for the Otter browser to develop. The latest betas are already rather functional and stable. Once mouse gestures are added, it'll probably become my primary browser.