Well, I finally got around to installing Rudeo's MCE controller on my 6700. I have to say that it is pretty sweet. I can control my Media Center PC from my 6700 from anywhere on my Wifi network. This may not seem like much, but think about this:
Load up an old PC with MCE and all of your music. Now, connect the PC to an old receiver\amplifier and run that to speakers throughout your home and even outside. Now you can be sitting on the back deck enjoying a warm summer evening listening to your favorite music. The kicker here is that the PC can be located you your basement, closet, etc. and you can control everything with your phone.
http://www.rudeo.com/mce.htm