I have had nothing but a horrible experience with WPMU. They make their site look so amazing and promise all of this great support and working plugins, but nothing could be further from the truth.
I installed the premium version of Membership and it was so buggy, the negative rules didn't work as stated in the documentation and it takes a great amount of customizing if you want it to work with other plugins that they offer on their site.
They over promise on their support as well. I have about 3 issues right now that are over a week old that their "support" people have just ignored. It is really outrageous how they market their support and products. I wish the WP community would really call them out more on their shady advertising and customer support.
Nothing but over promises. I am very much considering asking for a refund, but it looks like from other experiences, they don't make it easy.
I would seriously suggest people do a search for "WPMU dev reviews" before deciding to purchase one of their plugins or signing up for a membership. You WILL NOT get what they advertise.