The RRoD was essentialy solved after Microsoft started to use the 65nm Jasper chipset in 2008. I imagine the 720 wil be using closer to the 21nm process node technology by the time it comes out in retail, or at least 45nm.
In other words .... The ability to replace the cable box?
I have a tuner card with the ability to run media center with windows 7. But I don't.
A) flexibility of the video files for archive/management. But the cable company may be happy with it.
B) limited guide interface... Made for big screens only... Stupid. I loved using another DVR package which allowed you to have a 20 channel x 4 hour grid! Not a 4 channel 1.5 hour grid. But after market DVR software costs $100 and the big three have odd ball issues.
So I used the crap software that comes with the hauppange tuner... No guide. But it has a usable scheduler.