Is there a reason why you "had" to install Arch instead of using it straight out of box? Any instructions somewhere that will show how to set this all up with Hamachi?
Basically my needs are having a drive connected to it and share files back and forth (like dropbox) without paying any other fees besides this box.
Also, are there any other untapped potential for this device that I am missing?
A few other points about installing arch.
Arch is a full linux distro so by replacing the os with arch you are giving you access to many more applications.
For me I use mine to serve videos across my network to my blu ray players, tablet, computer via DLNA.
I can also have it setup as an SSH server so I can remote in to my network from somewhere else encase I need to access something or just want to say do some banking but dont want to risk doing it over open wifi.
A few other things I have seen people do: set up as a simple web server, torrent box, file server (via samba).