Well, yesterday was the first day that Comcast was making the new Microsoft TV-based DVR available to customers, so of course I rushed over there to pick one up. So, how do I like it, you ask? I'd say my initial impression is very favorable.
You can flip through the channels much faster than the previous system, and DVR feature is really nice, and there are a lot of options for recording series of shows. For example, you can record every occurance of a show, just the new episodes, only shows at a specific time of the day, and a priority in case there is a conflict with another show to be recorded. It is very easy to use, and the menus are really clear and easy to navigate. The picture quality seems to be much better than the old settop box (this may be because I never got around to hooking things up with S-Video cables.
This box is very high-end, with a wide variety of outputs including DVI, component, composite, and S-Video (I think I saw that!). Finally, it looks a lot cooler than the old box!
There is one thing that I don't like about it: the hard drive (I guess) makes a bit of noise every few seconds. I assume this is the disk heads moving (I believe the unit is always creating a temporary recording of whatever you are watching so you can rewind live TV). Normally, this is not a big problem, but when you are watching TV with the volume on the TV turned down low you can hear it.
If you do not have at least component video input on your TV (RCA jacks), you will either not be able to use this box, or will have to get some sort of converter; there is no coax output. As I said, this is a high end box designed for HDTV, etc., so if you haven't upgraded your TV in the past 10 years, it might be time to start thinking about it!
I think the DVR is going to come in very handy. I definitely like the menuing and the speed of the software. I may just have to get a DLP TV with a fan to drown out the sound of the hard drive!