GlimmerBlocker is a different kind of ad blocker. The problem with other ad blockers for Safari is that they are implemented as awful hacks: as an InputManager and/or ApplicationEnhancer. This compromises the stability of Safari and very often creates problems when Apple releases a new version. GlimmerBlocker is implemented as an HTTP proxy, so the stability of Safari isn't compromised because it doesn't use any hacks. It is even compatible with all other browsers.
You'll always be able to upgrade Safari without breaking GlimmerBlocker (or waiting for a new release); and you'll be able to upgrade GlimmerBlocker without upgrading Safari. This makes it much easier to use the beta versions of Safari and especially the nightly builds of WebKit. Because GlimmerBlocker doesn't hack Safari, there is a few things it isn't able to do: adding a block by right-clicking an image, stopping pop-unders, and filtering cookies from 3rd party sites. But you win a lot in stability, and GlimmerBlocker provides much easier methods for adding your own modifications to pages by adding CSS rules, pieces of JavaScript or by transforming the HTML before Safari receives it. So I hope you're happy with the tradeoff.
If you can program in JavaScript you'll be able to add your own modifications to pages. See the included filters for examples, e.g., adding a download link.
