Also I will add on top of that it is possible to use the Firefox adblock on Opera simply by exporting it's block list as a .txt file and add those blocked url matches (with wild cards being * ) into Operas url blocking system. And of course you can make exceptions so that the ads on your favourate sites (eg. daniweb) can still appear at your option. To do that simply delete certain entries.
ooor, you could just use firefox