Seriously,
There are so many directories out there and
I have joined and paid my fair share,
but when do I stop or when do I know that
this is a directory worth paying out for?

It is so boring drilling in my details to a directory
that will never be recognized on
yahoo site explorer or similar (suggest more?)

What do you think?

I believe the DMOZ and Yahoo directory are the 2 most important ones to have your site listed in. That said I have never paid to have my site listed in a directory.

Yes, the main problem is that lots of directories from only one IP address so this type of back links wouldn't work much.