I haven't tried using it, but I'd be
very surprised if it worked - the plugin framework (apparently) changes a lot between minor releases (3.0-3.1), so the change since 2.* would be marked.
Trying a plugin is (usually) quite safe, though. You just add folders to the 'plugins' directory and they're loaded, and remove them if you don't want them.
I've only once had a plugin really foul up. It was a PHP plugin (surprise, surprise), and it corrupted my whole workspace - a bit of a pain, but quite simple to restore.
So...if I were you I'd give it a go!
That said, I wouldn't like .java files opening in Eclipse myself - if I want to open one that isn't in an Eclipse project already, chances are all I want to do is skim the source and maybe copy a bit out (if it's in one of my old, archived projects) - and a lightweight editor like
Context is more suited to this. Still, each to his own!
Cheers,
-Tim