Since the Spring Update for the Xbox 360 you can boot your Xbox 360 directly in to Windows Media Center. This is great for people like me that use their Xbox 360 mainly as an Extender. It all adds to the WAF!
Thanks to Michael Creasy for the tip
The new Spring Update for the Xbox 360 is out.
While playing around with my system this morning I found a new feature I hadn’t seen reported before. You can now boot your Xbox 360 directly into Media Center. From the dashboard, go to System, Console Settings, Startup and there along with Disc and Xbox Dashboard is the new option, Media Center. Select that and the Xbox 360 will boot directly in to the Media Center extender experience when you turn it on. Great if you use your Xbox 360 mostly as a Media Center Extender.
The Digital Lifestyle 
You can also turn on your Xbox 360 and go straight to the extender by not using the power button for the Xbox 360, but just pressing the Media Center button on your remote. That will turn on the box and boot it to Media Center Extender.
Good point Keith!
Nice, I never new that. I hope IPTV will be out soon.