Well, Opera is now free. I got it a few weeks ago when they were running the 10th anniversary giveaway and have been trying it out as my main browser ever since. (Second used is Firefox, I can’t remember the last time I had to use IE).

Opera is not a clear winner over Firefox. There are some areas I like better in one than the other. Overall, I give the edge to Firefox, but just by a small margin - it is the ton of extensions that pushes Firefox over, not the core browser.

Here’s a little list of the things I’ve kept notes of:
Opera Wins:
RSS integration much better
Download integration better
Tabs retain last site opened
Seems faster
Bookmarks are nicer - especially like the ease of adding to a “sub-directory” area

Firefox Wins:
Mouse gestures are visible as being drawn
Can close the browser itself with mouse gesture (can only close last tab in Opera)
AdBlock extension is superior to OperaAdFilter
Custom Keyword integration better (vs. Opera’s search.ini)
Tabbed browsing - closing a tab puts focus on next tab (in Opera it puts focus on first tab)
Right-click search opens in a new tab (opera opens in same tab)
Overall customization much easier and more available.