Having never used a CMS system before, I'm just starting evaluating .net CMS systems, with the two most attractive options seemed to be Umbraco or Orchard.
Re Umbraco, I'd prefer to use the MVC flavoured v5, rather than spending lots of time learning XSLT for version 4.7, when that has come to the end of its development cycle. But, is now (May 2012, very soon after the release of 5.1) is actually a good time to start out on the Umbraco learning curve, as there doesn't seem to be the depth of support and documentation out there for v5 compared to v4? I'm sure it'll be improving all the time, but as it'll be my first CMS system, it seems a little scary leaping into a brand new, rapidly developing system.
Sorry for the subjectiveness / vagueness of the question, but any useful comments comparing the probable learning curves of Orchard and Umbraco 5.1 would be very much appreciated.