In the immortal words of Thomas Hawk, "Hot Donkey!" Update here. Update Rollup #2 for Media Center adds the following features:

• Xbox 360 Extender functionality. Customers can seamlessly access digital music, video, photos, and standard and high-definition television and movies on Media Center Edition 2005-based PCs through any Xbox 360 game console in the house.  (Come on, you know you want one...)
• Away Mode. Away Mode will bring the convenience, quiet performance and instant on/off functionality of consumer electronics to the Media Center PC.   (BTW: This is a kick-ass feature that almost all new Media Center PCs will have. Now you can save electricity and still record in the background or serve out to devices.
• DVD changer support. Media Center now offers integrated support for external DVD changers, enabling consumers to watch movies and manage DVD selections (up to 200) from the Media Center interface. (Ok, we all want DVD ripping, but take that up with the MPAA.  This just shows the team's heart is in the right place)
• DVD-burning improvements. Updates to the Sonic DVD burning engine improve the performance and capabilities of DVD burning in Media Center. Now consumers can convert high-definition TV shows to standard definition and burn to a DVD all in one step.
• Additional HDTV tuner support. Update Rollup 2 provides support for up to four TV tuners. Users will now be able to utilize two NTSC (analog) capture boards and two ATSC (digital) capture boards. (I'm not positive but I think you can do more than two NTSC tuners here as well ;)).  I'll double check.
• Performance Optimization. This update enables a new feature to "clean house" like most PVRs do today, Ed Bott has a good write-up on what this does here. You won't see this advertised, but it's a great great feature IMO.

Go to Windows Update and get your update.  Also a good time to make sure you have the latest Video Card, DVD, and Tuner drivers for your MCE.