One of the things I miss most from Opera 12 and earlier, was the ability to quickly add tabs to bookmarks, speeddial and etc, simply by dragging them. I've let the feature lie for long now, but with the recent introduction of bookmark syncing, I feel I can actually take the time to add all my bookmarks from my old Opera link account and add them to the new one.
However, as far as I know I can only do it one by one (Importing them requires installing old opera, exporting them and then importing again, and has caused troubles for me in the past).
So instead I'd try and see if I can get a long missed feature back. Currently if you try to drag another tab into your current one to add it to bookmark or speeddial, you will instantly switch to that one.
If there were a setting to disable switching to the tab until you let it go (I can't think of any practical reason for it to behave as it does, other than to appear a few milliseconds faster) instead of on first touch, it shouldn't be a problem managing bookmarks as efficiently as the old days.
I think this could get several more practical uses too, and not just managing bookmarks/speeddials quick and efficiently.
For example, dragging tabs into a text field could instantly copy/paste?
However to bring some good comments in here too, these last few Opera releases have brought the browser major steps forward, so good work dev team