Emir wrote the original SEF... there are too many ways to write it, and putting in extra features can add much overhead. Some want extra some do not.
-So emir wrote the "advanceSEF" - "compiled" with ionCube and speedy... sort of idiot proof. Commercial but cheap.
-Then there is the OpenSEF component - I have tested up to rev 4 presently. Open Source, "Free" lot of options... can be a pain, half idiot proof depending on how fancy you get with parameters.
There needs to be a better description for each kind of SEF in Joomla/Mambo, cause I thin everyone is confused on what SEF can or should look like as a URL.
Here is what I mean:
Here is a Joomla URL with no SEF on at all:
http://vistarealestate.org/index.php?op ... &Itemid=35
LONG HUH? ugly and not very friendly
Here is a Joomla URL with default SEF on (in global configuration/SEO tab ((and dynamic titles, just have to do with titles not URLS)):
http://vistarealestate.org/content/blogsection/1/35/
(so this is termed SEF, a little bit long and looks crawlable, I guess.... no - I know cause I've had good google SEO results with this)
Then with openSEF or advanceSEF on:
http://vistarealestate.org/news/
(Same link... believe it or not... also termed "SEF", but totally cool and somewhat troublesome as Joomla gets confused by component names and content items like Contact Us (Static Page) and Contact.)
I find for most of my sites openSEF works stellar.
Now what the stellar fellow and developer kawika was talking about was fixing this small confusion between content items and components IN THIS LAST EXAMPLE- properly, right now... not in the slower, wise, upgrade cycle in joomla stable.
My hack is in openSEF when it says something that conflicts go to the component admin of openSEF and use the replacement tab... and for anyinstance like contact or a duplicate menu item simply put in something similar like connect as a replacement for contact... your menu item will stay the same, but you'll notice the url "folder" will be connect. If this does not work... use Core Alias tab and clear what you did in replacements. Trial and error, depends on the situation. I've really had to muck with it and probably have an example of what you may be doing or trying to do.
Anyways, to summarize hours of reading the SEF saga... leave poor Emir alone. The guy is cool, he may well have to write a book on just why he did what he did, and does what he does and then record him reading it as a free mp3 for everyone. He is or was or still is in charge of the troubled task of developing core SEF for joomla in a balanced way. Everyone has a different opinion of what that should be.
There are so many issues. I am preparing documentation dealing with SuSE personality problems with modphp, and new issues with certain cgi's vs. the new htaccess file in 1.0.8 because of personal requests because of my posts here on the forum.... these ALL have to do with the issues of Joomla SEF.
OK. the windbag stops now.
-Matty
PS. Saw Kenmcd just posted while I was writing this. Kenmcd rocks.
He's openSEF which I use... note- good luck using advanceSEF for development site tryout... will not work with straight ip URL, locked to actual domain name! -oh well.
).
- just because it makes life so easy 
) :
