If you're really familiar with MoI you should be able to learn Rhino pretty quickly since the general overall approach is the same (like build curves, construct from those curves, do booleans, etc...).

The main problem is that you'll get annoyed more easily by trying to do things there because of stuff like 10 different kinds of snaps or special modes to use instead of just using construction lines, can't leave on object snaps all the time because center snap takes over, no preselection highlighting, 2D wireframe showing through all the time, inconsistent commands because of AutoCAD compatibility like with Split you pick the object to cut first, with Trim (AutoCAD style) you pick the object to be cut after, massive number of little buttons in the UI, etc...

You'll probably be a little irritated almost all the time but you should be able to get stuff done.

Rhino was just designed more as one little piece of functionality at a time all kind of tossed together, MoI is designed to solve more problems with a smaller number of tools.

- Michael