Paypal limits subscriptions upgrade price which is weird and totally agains subscriptions sites. For example if my user wants to change from a 10USD subscription to a 15USD, he can't due to this limit.
I saw other plugins avoiding this issue by deleting and creating a new subscription (see http://www.primothemes.com/forums/viewtopic.php?f=4&t=2566&hilit=20%25+rule)
So how i can solve this issue with membership? There is no point to have paypal if i can't upgrade my users