Yea I've heard a lot of people say opensef is the way to go. Its been awhille since I checked it out, but last time I looked at it a couple of months ago they didn't have a link for it on joomla.org extension directory, but eventually found the site through the forums.
I didn't like the fact that it wasn't llisted on joomla.org, makes me think that its not totally stable or somthing, pluss I think you had to do some code hacks to get it to work right. But again this was a couple of months ago.
As for sef advance I don't know anything about it, never paid attention to it, because I don't have the money to buy it and don't want to buy it. I gotta have a site that makes money before I will spend money on plugins etc, at least thats how I try to play it. I have heard that sef advance has pretty good support, I think, I might be wrong though.