While regular TV at 640 by 480 is not worth having. Get a ATI HDTV Wonder or 2 or 3, install recent version of Linux, and setup mythtv, and you've got a HDTV PVR capable of recording 1080i. Plan lots of disk space if you intend for long term storage. 1 hour of 1080i can be 8.5GB of space, and taking out the ads general only saves you about 2GB per hour. I did it, and it works great because all local channels have a HDTV equal in my viewing area.
Your solution only work for over-the-air ATSC signals. Many of us are unable to receive those signals and rely on cable, Direct TV, etc for HD content. These signals require a QAM tuner. The "HDhomerun" looks promising, but it still a work in progress from what I read. Currently, MS Windows XP Media Center Edition does not support QAM tuners either. So it is still rather difficult, if not impossible, to build a decent PC based HD PVR. Converting to Linux is an entirely different beast. For example, you cannot use XBOX360 as a front end, as I do.
Linux support for HD and QAM is much better than Windows. You can get the (linux-only) PC-HDTV card for regular and HD TV including QAM. And it ignores the broadcast flag (DRM) too so you can save all HD programs.
Linux and MythTV are both free for download, and have way more functionality than Microsoft Media edition, and also just about any other commercial product.
Throw it on an old PC and subscribe to TVXML for a free tv listing service, then you have all in one the functionality of an HD TIVO, a DVD player and recorder to copy saved movies to DVD, a CD/MP3/OGG player, a games machine, online weather & TV & News listings and web-surfing all from your couch and without any monthly fee.
I made mine out of my old PC after I upgraded, and bought a nice home theater-style PC case for $50. It looks really professional and expensive.
It boggles my mind why this isn't way more popular. MythTv can be a pain to set up initially, but you do it once then you're done for ever. It seems people still prefer to buy a Tivo (or much worse, a windows media edition PC) and pay a monthly fee for much less functionality. Most people who come to my house and see my system usually can't believe how good it is and how it doesn't have a monthly fee.