David from Artio has helped me a lot and very quickly. I was amazed because he didn't care if I had bought his extension or downloaded for free. The support was efficient and replied quickly...
I used to install OpenSEF in my sites, however it has three issues:
1 - OpenSEF + MTree issue: All Brazilian Portuguese special chars didn't get the equivalent English char, so in the url "ç" becomes "%e7", NOT sef at all :(. JoomSEF works with the special chars out of the box... Now with JoomSEF "ç" becomes "c"... AWESOME!!!
2 - Writing the sex_ext.php: That was so annoying! In my opinion it is much easier to write the com_component.php files in the JoomSEF style!
3 - Every time I installed a new extension I had to configure openSef in order to start making the URLs SEF. JoomSEF is automatic.