Hi.I want to recommend Wpmudev because of their professionalism and honesty.
They are professional because they have in their team a bunch of people that they know where they are and what they do.
When i start working with them i have a lot of doubts about wordpres, i have really started with them and they were there to help me in all of my issues and no one of my questions remain unanswered.
Furthermore they have the biggest repository of plugins and themes that i have ever seen. Near to you at one click away. Plugins that make your life very easy in wordpress. Even plugings that suggest you new ways of business that i have never think about. For all of this I fairly recommend wpmudev.
And for their honesty, something very important when you make business in internet. They fulfill everything that they promise. And even something like to respond in less than an hour, something very important when you are in a problem, or something go bad with your site.
For all of this I recommend WPMUDEV.