AFAIK, Opera is one of the most popular browsers throughout all of Eastern Europe (I think it's #1 in Ukraine).
From what I know, a large part of this is that back in the day, internet connections in those regions were so slow that Opera's feature set (which at the time was far and away better than other options) made browsing a much better experience. It aggressively cached content, allowed easy access to disabling images, didn't automatically reload pages while navigating back through history, etc.
IE - 32.0%; Firefox - 26.3; Chrome - 7.3%; Safari - 0.8%; Opera - 23.9%; Opera Mini - 8.5%.
This is from liveinternet.ru, the most popular site tracker (visitor counter) in Russia. http://www.liveinternet.ru/stat/ru/browsers.html?period=mont...