After installing a few extensions (adthwart, sidewiki), I've noticed some problems, so I'd say that the implementation is still a touch buggy. But, still, this is an awesome step forward for Chrome.
Has Io been useful in any application yet? Admittedly, I find it an interesting language, and my experience with it has been kind of fun - but I can't think of anything it does that most other programming languages don't do better.