Pre-registered during the beta to secure the final release at the lower price.
Though Silo has an amazingly customizable interface, some of the places they stopped short on the features you are able to change make it feel somewhat "half-done". (Little annoyances like being able to customize the colors used in the UI, but not all of them such as the display of the normals.)
For the price it is a great tool. I was very easily able to mimic a large part of Wings3D's UI (my preferred but somewhat stalled development wise modeling app) Again though this has been some issue for me as each new beta would not load the keybindings and layout I had designed from the previous version. Bugs went unanswered on the forums at Nevercenter's site. Each time there was a new release candidate, this and many other problems persisted on the Mac. It hasn't crashed on me yet, but that doesn't mean that the last RC was a viable candidate for 2.0 final. In my opinion, it was not. Perhaps it is less buggy on Windows? I need to check that soon as this is another good thing about the company - your one registration will let you use Silo on Mac and Windows. A nice little bonus.
Personally, I am hoping 2.1 fixes some of these issues and the many others I have come across that keep me from using Silo all the time. I am happy I paid though to help its development.