This sounds very promising and interesting--a robust cross-platform GUI-development platform. However, I've always been a bit baffled by the idea of Mozilla/XUL as a "development platform." It is so unlike the environments I'm used to (Tcl/Tk, AppleScript/Cocoa, Python/wxPython) that I'm not clear what one does with it. So here are some questions:
1. Can one do general-purpose GUI application development with Mozilla/XULrunner--using JavaScript instead of Python or Tcl as the programming language? (i.e. is there finally a good reason for a non-web-dev to learn JavaScript?)
2. Does developing with this environment require one to do hacking in C++? (I'm not interested in hacking with C++.)
3. Can anyone point me to applications that already exist that make use of Mozilla as a development deployment platform? I'm already familiar with Firefox, Thunderbird, and Komodo. Are there any others? (i.e. that are standalone apps and don't run as Firefox extensions, say?)
4. What kinds of applications are *not* feasible with this development platform?