Starting with v.10 -- which is now available for Windows, Linux, and Mac -- Arora ships with AdBlock pre-installed. Unlike Opera and Konqueror which allow for manual blocking by default, Arora utilizes subscription-based blocking out-of-the-box. Arora's developers claim this is a first for web browsers.
Arora also now includes a wallet (or password store) feature and a handy set of address completion hotkeys: ctrl + enter appends .com, ctrl + shift +enter adds .org, and shift + enter does .net. The new version also includes a number of bugfixes, which you can read about in more detail on the official blog.
Even with two fairly key additions, Arora remains very nimble and easy on system resources.