1. Any extra parameter cannot be handled in JoomSEF. If there is extra parameter then the whole site will become blank(a pure white screen).
2. In Joomla 1.5 we have a option to Filter "Archived Articles" in frontend, This is not working after installing JoomSEF
There are some more issue still which i dont want to mention here, may be all of these are because of a single problem.
I personally feel that this component is not worth buying.
I think that is not true.
We are using article archives on our own site and they work just as they should.
So the problem may be in some speific configuration of your site.
Also, handling of extra parameters in URL work fine, if you configuration (filtered variables, non-sef variables, etc.) is correct.