I see the new Desktop class (which I'd like to use for its browse(uri) method) includes checks to verify that it's supported. If I'm distributing my application for multiple operating systems, should I expect that it will sometimes be unsupported, and stick in code like this "Bare Bones Browser Launch" as a fallback method, or would that be extremely rare? Any particular OSes for which I might expect problems?
(I'm distributing for Mac/Win/Solaris/Linux, but feel free to answer about any exceptional OSes if you know something about them.)
You should program defensively.
From How to Integrate with the Desktop Class:
Use the isDesktopSupported() method to determine whether the Desktop API is available. On the Solaris Operating System and the Linux platform, this API is dependent on Gnome libraries. If those libraries are unavailable, this method will return false
(emphasis mine)