Exceptions related to loading xulrunner should be handled right way. Human friendly messages would be good here for usecases we know. VPE should check for current platform and if it is not supported do not scary users with exceptions. It should try to load XL just in case path to XL injected outside through System property, but show explanation instead of just exception. Something like:
"Current platform ${os}${ws}${arch} is not supported. To find list of supported platforms and possible workarounds. please read this article on JBoss Tools Community Portal". If someone is trying to inject XULRunner implementation using system property it can say, That "Visual Editor tried to load XL from provided loaction ${pathToXulrunner} but it failed with exception, please find it in Eclipse Error Log View".
We could also have check box to remove VE related parts from editor:
"[x] Open only source part of Visual Editor".