Tried out the GData Java API. It works fine with Blogger, even though it's slightly cumbersome to constantly have to manipulate strings to extract the "real" id of any given object; it would have been nice to have some sort of dictionary structure, like this:
but I guess that's way too nice for the java world! :)
The more I think about it, the more the idea of a jEdit plugin for blogging makes sense. It would just be a matter of writing lots of scaffolding (options screens, layouts etc), like you always have to do in Java. Is there an equivalent of Qt-Designer in the Java world, where you design your interface, save, and get a nice class ready to be used? That would speed up things immensely.