I've started playing with zombie.js recently as well - much lighter and faster than the ones that instrument a completely full browser. But has a full Javascript engine.
I worry that it's not going to replicate a real browser accurately enough, but I'm excited to try it out a bit.
We're also trying it for integration tests, as it is much quicker than Phantom or Selenium. Even there, where we control the standards-compliant site, it isn't quite good enough yet.
Would love to see more people helping make it so, though!