It doesn't have the essential Adblock Plus of Firefox but it does have something similar, 'blocked content', which enables you to say 'don't bother trying to load anything with this URL'.
So, looking at a Guardian article, I want to block the annoying mid story ads. OK, right click to get the relevant link, and paste into the Opera list. Coo, that's a bit long.
The only bit that's needed for this purpose is ads.guardian.co.uk/* (i.e. anything at ads.guardian.co.uk, thank you for making it so easy to specify what's an ad). The rest included this bit:
plus the URL of the story it was advertising. I wonder what all those 'values' mean...