Do the desktop and laptop have the same OS?
Right now the save to disk feature saves the metadata as an OPF file, in the same directory as the ebook files. When I implement recursive ebook import, it will import the metadata back into the database as well.
The equivalent of browsing through a folder structure in libprs500 is to use the search, so for example if you want to browse books by Asimov you type author:Asimov in the search field, then if you want to browse books tagged with "foundation" you type "author:Asimov tag:foundation" and so on...I find this a much more powerful browsing system than using folders. After all folders are basically hierarchical tags. But general tags, like libprs500 has, can mimic the functionality of hierarchical tags and provided more features as well. For instance, if you want to browse through books by two different authors, say Dostoevsky and Russell (don't ask me why those two), there's no convenient way to do it using folders, but with a search interface you just type [author

ostoevskt author:Russell] and then you can sort the list on title or date or rating and browse through your collection easily.
EDIT: I hope your girlfriend isn't reading this ;-)