According to Google, Octane introduces five new benchmarks that have been "created from full, unaltered, well-known web applications and libraries."
As always, the benchmark results heavily depend on the hardware you are running, so I won't make any performance claims for any browser until I have run them in at least a dozen different hardware configurations. However, my first impression on four systems seem to indicate that the dominance of Chrome in V8 is extended in Octane. Firefox 14 are 15 is up to 90 percent behind on single-core hardware, while the IonMonkey equipped Firefox 17 NB reduces the distance to as little as 35 percent.
It is still an incomplete benchmark and, for evaluation purposes, it is wise to use a combination of several benchmarks to come up for a more realistic score. I have complained in the past we lack an industry standard benchmark for browsers and Octane is just one more sign for that.