[stonemetal]

I wouldn't recommend it if you want to get something done. It is an interesting way to explore the set of features they have chosen for the language(Prototype based OO, meassage passing, code easily modifiable at runtime). The point of the language seems to be more art than tool:

Io's purpose is to refocus attention on expressiveness by exploring higher level dynamic programming features with greater levels of runtime flexibility and simplified programming syntax and semantics.