Well i'm afraid im not so creative when it comes to my wl700gE. I use it as a NAS of course, i think its pretty nice to have my entire media collection always available
I also use it as a media server through mt-daapd, which serves music for iTunes and a "web player" called FirePlay, so i can access my music when i'm not home
I used to use it for downloads too, but i just felt it was too much a of hassle. MlLDonkey+Sancho just can't compete with uTorrent.
I would want to serve as a uPnP server for my xbox 360 too, through Fuppes, but unfortunately i can't get that to work :x