If you build from the master branch you have the latest stuff. We recently released Designer version 2.1 and will release 2.2 once we have fixed any reported bugs and also have plans for new features.
jBPM Designer is currently not supported on IE. Designer is at its core a very powerful JS library for SVG manipulation and IE has notoriously not been able to have proper support for SVG. I have heard that some community people have had success on IE with Chrome Frame installed so you might want to give that a test to see. We test Designer on FF and Chrome and until we add support for IE I would suggest you use those real browsers :)
HTH