It basically feels like Java's checked exceptions without stack unwinding and with a nicer syntax - the possible errors are part of the signature, the compiler insists you do something about them, and there is a wrapping facility to cross system boundaries without leaking details.

In case my comment is taken as denigration, I'm saying this from a perspective of admiration. I think this is a fairly elegant way to solve a difficult problem, and learning Rust has been a true pleasure. I'm excited for the future of the language.