That dev branch is unstable and it has not been widely tested.
The dev branch takes the current master and then changes the system from using a div with everything nice and pretty for it, to an <audio> or <video> element and it gleams the info from the page. In most cases this will work fine, such as if you gave the type for the source elements.
As for a playlist... We been focussing on getting it working for single instances. This will satisfy the majority... But will still leave those who want to put 20 on the page with issues in browsers like chrome.
We'll keep the playlist thing at the back of our minds though... Before making the "change" in dev branch, I had been considering making the injector have an option to use 1 jPlayer instance... So this is like the playlist.
But we have to make decisions... And the decision is to make the injector a polyfill for the HTML5 media elements. It is the most straightforward and makes it easier for unskilled people to use it. You know, the old slap this 1 line in your page and we'll take care of it for you type of solution. Thus bridging the sometimes overly complicated jPlayer API with a straightforward 1 liner solution.
BTW, we already have the moustache templates for the [dev branch] injector added to the skins we sell on
jplayer.it all ready for it.