Is there somewhere a list of components and modules that are know to work
(a) without any modification
(b) with some modification
?
This would be handy for everybody. There is a very short one on the download page or somewhere else, but it cannot be updated. It would be nice to have some way to have an up to date version of this list. There a many, many extensions available for joomla, and it would be really great to have a big list of those who do not have problem at all. Isn't it ?

We have no list because the customer does not inform us on the extension they use.
We already sent email to the customers to receive such information and unfortunatelly, we have received very few answers.
The list we have provided on our website (front page and product detail) reflect the information communicated by some customers.
Perhaps you will receive a reply from the JMS customer concerning the extension.

I have JoomlaWatch and it seems to have stopped working on my site after installing Multisite. Any ideas? This is the error I get on Joomlawatch

Notice: Undefined variable: droom_sub_sub_sub_sub_domain in /raid/serv/httpd/htdocs/joomla/administrator/modules/mod_admin_user_access/mod_admin_user_access.php on line 0

Ignore this message. It seems that the issue is with admin-user-access, not this component!! Sorry!