I know that it is possible to get a RSS feed per category/forum, but it is not really useful.

It would be better to have the possibility to select forums where to get RSS from:

Like: rss.php?forumids=2,6,77

Will you implement a feature like this?

#include <rst>

Don't anyone else think this would be useful?

I think a RSS feed is a required feature from a forum suite... 

Does anyone listen to users who pay for this software?

Yes. I support your view.

It is a must feature to be able to select forums where to get RSS from.

And the feature was there in earlier versions.