Discovered WPMU DEV while looking for support with my first steps in WordPress Multisite. The membership of WPMU DEV offers huge value for your money. I have to admit, so far I only used their plugins. They have loads of them. The plugins for Multisite work like a dream. For me it made my start as a multisite user so much easier and better,
I also tried the 7 themes of WPMU DEV and their Theme builder. So far handling them is too difficult for me. Have to put more time in that, but that will come later on.
Finally, the support of WPNU DEV is excellent. Only negative side, it took some time. But the ability of the support contributor to explain everything and his tone of voice was excellent.