Opinions aside, this all depends on your background. I'm a software engineer not a webmaster. So, I think like a software engineer and not like a webmaster.
Umbraco was VERY frustrating for me to install simply because there was no easily found TEXT documentation. Once I finally found that, it was a breeze to install.
The problem for many web designers is that they are not software engineers. Nothing bad about web designers who aren't also software engineers, it's just a different way of seeing the world. I have worked a lot with web designers who needed to interface with my C++ and C# back ends; they have a completely different perspective of almost everything.
Once I got past the goofy implied install process (which is bad, bad, bad -- you should never require another product JUST to install your own!) I found Umbraco to be simple and intuitive. Even my (non-programmer) girlfriend found it to be much more logical than some of the other CMS's we had been playing around with. Drupal, for example, was simple to install, but isn't really designed for a Windows development (ASP.NET/SQL Server) environment and I hate PHP, so I eventually abandoned that. MojoPortal was really nice and simple, but... it was... well... simple. Too simple.
I like Orchard, but the last time I looked at that there was so little in terms of what to start with that I decided that it would be a problem in the immediate future. I wanted a web content management system, not a web development platform. I kept thinking Orchard is a lot like *nix: "A nice place to live, but ya wouldn't wanna visit there."
Umbraco for me is a nice medium place, extremely flexible and easy to extend. It tries very hard to not get in your way. If you want to extend it you would probably do best to either learn C# (or {cringe} VB) or co-opt someone to write the CodeBehind for you. But, using it is extremely simple and straight forward.