What does the menu do, other than the obvious ?

At the moment, there is a wallpaper switcher in there, but not much else

But in future versions, it will be handling things like portable fonts, environment vars, file associations, url handlers, and more.

If you are launching docs from explorer, make very sure that you are associating the files with the launcher, not with the base app, as the launcher is the part that does the magic that makes the app portable.

Right now the menu offers automatic language switching for the Apps who support that. As english isn't my native tongue, I like that because I dont have to set the languages of all the programms manually.
But I know this probably isn't such a big thing for english-speaking users.

So, changing drive letters to accommodate the letter of your USB drive, and cleaning the registry and temp files, are all done by the individual app's launchers.

Portable Fonts, File Association, PortableApps Updater and other planned enhancements for the menu were started as separate apps.
I think the Fonts app is dead, but there are two File Association apps - eXpresso and PortableFileAssociator.

For at least two apps, you can add fonts directly into special folders to take your special fonts with you (OpenOffice and GIMP).

For me, I like the ability of the menu to auto-start apps when the menu starts.

P.S. I'd love to see Portable Fonts and these other apps developed and continued as independent from the menu. It would offer these functions to non-menu users, and we'd likely see them sooner.