Well regarding the special sale, without naming anything specific, most of it appear to be exclusives that are normally only available in a single country, distributed through a museum or made for a specific brand as promotion or such.
Don't expect any big sets here, it can happen but it would be an exeption to the rule.
I'd say that the free yearly clicky that is uniquely made for PCC members and that special sale that will allow you to get some international sets for a normal price instead of rediculously overpriced in the second hand market make it all worth it. And on top of that you get lots of information and get to vote on polls too.