The IoC threads work by converting park-able functions into Single-Static Assignment (SSA) form [1] and then compiled to a state machine. Essentially, each time a function is "parked", it returns a value indicating where to resume from. These little state machine functions are basically big switch statements that you don't need to write by hand. This design is inspired by C#'s async compilation strategy. See the EduAsync Series [2] on John Skeet's blog, and the compilation post [3] in particular. Once you have these little state machines, you just need some external code to turn the crank.
My impression is that the IOC threads spare you from needing to write continuation-passing-style code by hand and let you program in a more idiomatic style instead. This would be specially useful if you have lots of jumps in your control flow such as loops, return and break statements.
