I tried the latest Nightly, Aurora and v6 Beta yesterday. Couldn't run the nightly well, too much weirdness caused due to the changes in the UI. Aurora did feel snappier, I'd just come off reading a review that it was targeted towards performance, so hopefully that wasn't the placebo effect. v6 Beta felt kinda the same as 5, couldn't tell much of a difference. Roboform doesn't work on any of these, even after manually bumping up the version in the .xpi. I'm back to v5 and really looking forward to Aurora getting out of the pipeline.