
The upgrade will feature many new and improved features such as an improved CSS3 engine as well as a totally new JavaScript engine that will improve the rendering of many pages and also passes the CSS3 Selectors Test with flying colours as you can see on the image on the bottom.
Other features are a tweaked user interface to provide users to access their most often used options and buttons. Keyboard navigation will be improved as well as the support for Screen Reader. Also for the Mac and Linux versions there will be new skins to make the browser feel more at home and for Linux there will be 64-bit Linux/FreeBSD packages made available.

The final feature to be improved is the speed; Opera 9.5 will be far speedier in benchmarks as well as actual web pages compared to previous versions.
Source: Opera Desktop Team Blog