xrumer

Ok this software seems pretty popular with the members of this site.

But there are also a lot of warnings to be careful or you will get banned/sandboxed.

So my question is
a) when is a site ready for xrumer (PR? backlinkss? etc.)
b) what is the best software to use to get a site ready for xrumer

thanks

seems like someone should have a good number in mind...