Currently if you want to make Time Machine backups, you'll have to
jump through hoops. (Note: You will most likely fail in getting through that how-to, that was just an FYI)
I haven't tried streaming movies from it, so I can't say anything about that (I prefer moving so large files onto my computer before playing them; if I watch HD quality movies over the wire, my itty MacBook can't handle the infinitesimal extra load).
If you have the need, you can follow other tutorials on abovementioned site and get stuff like a bittorrent client onto your NAS, get a better FTP server than the built-in, plus much, much more. That is, if you're a nerd. If you're not, just use it as D-link has set it up, that's still a pretty sweet deal.