After all these years of development, Firefox on a Mac still doesn't feel like a true Mac app. Text fields, for example, still don't work like Cocoa text fields.
So all this portability comes with a steep price of never really having a superb UI on your target platform.
Take a look at Songbird... it's been in development for many years and a lot of that is due to XUL. I'm pretty sure that had they chosen native widgets on each platform (GTK/Cocoa/MVC), they would have finished it faster and had a much better product overall.
But the lure of "write once, run everywhere" is an everlasting dream that almost never comes to a realization. Take Java for example... it still has platform specific quirks.
So all this portability comes with a steep price of never really having a superb UI on your target platform.
Take a look at Songbird... it's been in development for many years and a lot of that is due to XUL. I'm pretty sure that had they chosen native widgets on each platform (GTK/Cocoa/MVC), they would have finished it faster and had a much better product overall.
But the lure of "write once, run everywhere" is an everlasting dream that almost never comes to a realization. Take Java for example... it still has platform specific quirks.