I have the same kind of problem and situation - I also use Opera and i have 3 different inconsistent things I use none of which is perfect. My main constraint is that it needs to work off a key or the web, because a key function is to be able to capture something that comes up while at work or on the road, and capture it
what i use:
- diigo. bookmarking with highlighting and snippets + can keep a cache of pages (not 100% reliable alas). Just not enough that can be done with it afterwards if you are aggregrating for writing or organising (lists, groups and slideshows, good for sharing but not for writing, imo). Has great extensions in other browsers and a more limited diigolet in Opera. Perhaps it will port its extensions to Opera
- opera notes. very simple but because it is sync'd and accessible at my.opera.com it is extremely useful for all sorts of tidbits of information and often to write/prepare for writing. The capture from opera *and* the fact that they can be used as quick paste tools mean I use them all the time... I really should see whether something can be done to access/manage opera notes on the desktop from one of the outliner tools perhaps, that could be very interesting
- local website archive - a bit clunky to capture from opera and alas can only do full page, so I use it less than I once did due the the clutter it generates. I used to use it all the time as my main tool but it kind of stayed behind in time.
So I am looking at tools too