I mistakenly deleted this post from andrey.
This problem was introduced with beta4:

When you declare AppEvent as follows:
new AppEvent<String>(AppEvents.Init, "foo")
you get a compiler error that this is ambiguous with the new AppEvent(int, String) constructor (this second ctor takes a history token as the second param). This forces me to create an intermediary class to wrap the String as a work-around.

The AppEvent(int type, String token) has been removed from AppEvent. Fix is in SVN.