After 10 years in the market, Opera is still very much a minority browser. It’s the only one of the big browsers which display adverts and then tries to charge you to get rid of them. Oh, and they display Google targeted contextual adverts so I presume they send the URL of every site you visit to Google. Newcomer Mozilla Firefox has been a huge success and currently has a market share of somewhere around 7-8%. Firefox forced Opera to go through quite a UI overhaul in Opera 8.
There is now much speculation that Opera may become free (i.e. full program without adverts for free). This would certainly be a very good move for Opera especially if they’re going to compete with the likes of Firefox and Internet Explorer.