I'm very glad opera will finally support extensions. Hopefully it will provide a better interface for tackling ad blocking than the built in blacklist feature or doing it elsewhere(proxy,dns,etc.).
Personally, I've never found the built in ad blocking lacking. Where it missed anything (which is rare), blocking a specific ad is two clicks or so away. In what ways would you like things improved?
For me most useful would be subscription to some EasyList or whatever it's called to block 90% of the ads.