Unlike some of the other comments on here using the free themes and not getting access to essential features, I actually purchased a $39 membership and STILL don't have access to all the features of the theme I bought. What's worse is that Nimbus advertises 'support' yet I've contacted them twice and still no response. In my last email to their customer support I requested a refund for false advertising. We'll see how much they're concerned with their quality of service. WordPress should not affiliate themselves with Nimbus!
Avoid at all possible costs.
As others have pointed out, this "free" theme is anything but. You can only do the most basic of tasks without having to pay to be able to modify areas of the theme that every other free theme allows you to modify. WordPress should not allow this to be a choice of one of their free themes. BOOOOO NIMBUS.
Why offer a theme and not mention that the only way to truly customize the theme is purchase a membership? Uninstalled!