Well everyone I know including myself has had a heck of a time getting an SEF component to work. As of right now my favorite is ArtioJoomSEF component, but I would like to see the new version of Joomla include a couple extra features for instance, I want full control on how the SEF URL is formatted, and how precisely the URL will finally appear, even after edits. Let's say, for instance, I need the SEF URL to include the section & categories name in the URL, as that's how I divide my contents. Problem is, Joomla 1.5 RC2's SEF features are not consistent in URL creation, sometimes they include and then later exclude the section/category names.
While giving full control on SEF URL creation, SEF should be able to check for duplicate URLs or content & suggest a unique SEF URL for our title, just like an SEF feature on Wordpress or similar.