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 create problems when Apple releases a new version of Safari.
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.
In this detailed guide on how to block pop ups on Mac, you will find the best ways to easily get rid of annoying pop up ads regardless of browser type.