FF perhaps isn't the easiest to organize bookmarks, but I don't see it is that difficult.
Going to Bookmarks > Organize bookmarks takes you to a new window titled Library. In there you can add new folders, drag and drop folders and files elsewhere, and delete files/folders.
I agree there is no easy way to rename a folder, an oversight on the part of Mozilla I feel, but the workaround is to create your new folder with the name you want, then cut and paste the files/shortcuts from the old folder to the new one. You can even highlight all the file/shortcuts, and drag them to the new folder.
Is that what you mean?
I have Windows XP Pro, sp3.
In Firefox 2, doing things to your Bookmarks was apparently much more intuitive than in 3. In Firefox 3, there is seemingly no way to do things. In IE 7 there is a button in "Organize Favorites" to rename a Favorite but I can't figure out how to do it in Firefox 3. In IE 7 there are also buttons for "New Folder", "Move" and "Delete." I originally started this because I couldn't figure out how to rename a Bookmark. Now I know there is other stuff that I used to know how to do in Firefox 2 but I don't now with 3. Does anyone know how to do these things?