Subscription recently introduced, not too fond of that - even though most features users are interested in are still free.

Still a great add-on.

Will see where we go from here I guess.

it works great many times, but not very rarely it will simply NOT send any header added.
I would like to report this as a bug: it sometimes repeatedly will not send any header, even after restart of firefox.
In Chrome i did not have such problems.

Works great on Chrome, on Firefox however it will not modify the header of a POST request made from a SWF file.
It modifies the referer for "Request Headers", but not "Request headers from upload stream".
(yeah they are 2 different things with unique headers from a single request)