Some time ago I tried the Xaneon SEF extension and it bombed, now that it has evolved and the development is more open, it comes back with a new name: OpenSEF.
Just installed the component, configured, and it just worked (with minor glitches due to remnants of the old Xaneon data). I am not sure it is more search engine friendly, but it sure is more wetware friendly to have URLs that are derived from the article's titles, etc.
It has some nice features, such as a unified URL mapping, and even support for multisites (which lacks a bit of documentation, but it is something very powerful).
Everything combines to make OpenSEF a highly recommended extension for Joomla.
Manteniendo la casa limpia: Probando y depurando aplicativos en PHP 
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