Great idea! I love ABP on my computer, so naturally it was one of the first 'apps' I installed when I got my N900. Unfortunately, it doesn't work after install without significant extra work, so I too think that it should not be in extras. I expect apps in extras to work out-of-the-box with little or no tinkering. IMO, still devel/testing quality.

Here's how I got it to work: - Manually installed version 1.1.1 from http://browser.garage.maemo.org/extensions/adblock_plus-1.1.1-fx+sm+tb+mb.xpi (1.0.2 didn't have Easylist preinstalled) - In the browser, type about:config, find extensions.adblockplus.enabled and change to "true".