Actually, i disagree it's a bad idea to have two devices; I trust that the apple extreme will work fantastically to share a disk for me; they get the OS and the fs, so it's pretty straightforward.

A one device solution? Well, that'd be a router, switch, hard disk... (can you say, computer?)

sometimes we want stuff that's single purpose, done well, easy on the power/heat/etc. I now have an appletv on a turn-off power strip, enabling me to 'turn on' the tv system and have something running easily, rather than having to get my laptop out, an external disk, try and make it all work. Ugh. madness.