Like any other browser Opera has many options to let it be configured precisely to your likings. This is done through the usual interface as well as through a configuration page just like Firefox' about:config.
A great deal of options is already offered in the preferences accessible by going to Opera > Settings > Preferences.... Apart from the usual actions such as form premades, text formating and search engines I'd like to point out a few that might come handy:
In Preferences, go to History on the left pane and set Check images to 24 hours. This lengthens the time span that images are stored in the cache, so they don't need to be reloaded from the page if you reaccess it.
Afterwards, go to Browsing on the left pane. The option Smooth scrolling gives you a better feel about scrolling, but will most likely cause speed issues with some sites. It's up to you what you prefer but if you go for performance better disable it.
Close Preferences now. If you need more space for tabs, you may consider right-clicking the tab bar and choosing Customize > Appearance.... Go to the Toolbars tab and set Wrapping to Wrap to multiple lines. This will expand the space you have for tabs vertically.
If you want more options, enter opera:config into the browser's url bar. This will give you a long list of them which, howeverm want to be handled with care.
If you don't like Opera's mouse gestures for example which appear on holding the right mouse button, simply go to User Prefs > Enable Gesture and untick the box.
Documentation for most of the values can be found here: http://www.opera.com/support/usingopera/operaini/