The lack of active noise cancellation still seems to leave Google a "generation behind" here, but playing catch-up is still a great thing.
But more than anything, I'm fascinated by the "Adaptive Sound" mode. Seriously, for years I've wanted my headphones (and laptop speakers) to auto-adjust their volume based on both the signal and ambient noise. If it works well, I hope to see the concept spread pretty much everywhere as an option.