Random list of a few features of Opera that help set it apart from Firefox. Not that firefox is bad… Opera is just that good.
Smarter Tabs
If you hover over tabs you get a previews of the content on that tab. If you grab the resize control of the window to give the tabs more room, you get full previews of all the tabs at once.

much smoother integration than with Firefox plugins
Opera turbo - on/off/automatic
You can control how often the cache is updates for images and other content.

Configurable Cache
Individual control over memory cache and disk cache
Opera mini
The data is compressed before being sent to your phone. And Opera was the first and has always been the best mobile browser.
Opera Dragonfly
Debug javascript, css, and html all in one place

Speed Dial
I like having a few bookmarks at my fingertips with previews of each one as soon as I open a new tab.
All the little things
I keep running into new little features, like middle clicking links to open them in new tabs without opening that tab.
Posted by admica @ 9 September 2009