
The auto-completing command line and the ability to enter exact values of what you want any tool to perform. The way I explain Rhino to other 3D users who don't do CAD is: Rhino is basically an incredibly sophisticated DRAFTING tool: it's not only my favorite 2D drafting tool, but it's the best for hard surface 3D modeling projects as well (or any modeling that will then result in physical prototyping and manufacturing). Rhino has a unique UX due to its command line, and it's very much appreciated. Review collected by and hosted on G2.com.
For my uses, I've never found a single significant shortcoming that is worth griping about. Really, Rhino is like an old friend.
Better line and fill visualization options would be handy, but I'm still using v5, so maybe 6 or WIP has some of this already. Review collected by and hosted on G2.com.