Among others, many will rejoice for the availability of Function.prototype.bind (bug 10522), something that is missing from the old QtWebKit in Qt 4.8. There were various attempts to solve this in the past, see my previous post to the mailing-list. However, as I wrote there, sometimes our collective effort was not enough to move the mountain.
Another related improvement is the handling of the special object arguments. Just like other modern browsers, now you can JSON.stringify this object (bug 11845), use in a for-in loop (bug 11558, bug 10315), and call Object.keys on it (bug 11746).
PhantomJS 2 will be released whenever it is ready (monitor the mailing-list if you want to get notified). Meanwhile, if you want to compile it yourself and play with this bleeding-edge version, follow the step-by-step instructions. If you are on Linux or OS X (like typical geeks these days), building it yourself should take just 30 minutes on a fairly decent machine.
Good things come to those who wait!