[Update: check out Signal GH, an iPhone utility for monitoring the signal quality of an HDHomerun].
One of the best bits of tech I've bought over the last year is the HDHomerun networked digital HDTV tuner. I was reminded of this a couple of weeks ago, when I was going through the process of setting up a Mac Mini as a dual boot Leopard/Vista desktop.
The OEM copy of Vista Home Premium I picked up cheap at MicroCenter comes with Windows Media Center, which Silicon Dust supports for use with the HDHomeRun, so for no added cost, I get live TV watching with a guide, and recording. This is functionality I would not easily get otherwise, as there is no MythTV client for Vista, and I am not going to get an additional tuner for the Mini. It just happened I get all this for free because I happen to own an HDHomerun.
Not that I'm very impressed with Windows Media Center, at least not on the Mini. HD playback is a bit stuttery, unlike VLC on the same OS and hardware; and navigation is confusing. Also, there doesn't appear to be an integrated solution for using my Wiimote; Remote Buddy on the Mac spoils you for effortless couch potato style navigation. MCE does allow the same application to control both live TV viewing and DVD playback, whereas I have to switch off between EyeTV and Front Row on the Mac, but that is comparatively easy with Remote Buddy.
Another HDHomerun nicety is that EyeTV can Picture In Picture both HDHomerun tuners (again on the same hardware Vista MCE can barely decode 1 stream), allowing me to watch 2 HD football games simultaneously, which will be my preferred mode going forward. I like to watch football live, so EyeTV wins over MythTV, whose live TV support is always a bit cumbersome, and the PinP feature seals the deal.
Anyway, my main point is to emphasize the value one gets from a networked device. Because the HDHomerun is accessible from any computer in my house, any computer capable of decrypting an HD stream can use it. In my case, I have 3 computers (my MacBook, a Mac Mini, and my Linux server) and 3 operating systems (Leopard, Vista, Linux), each with their own strengths, sharing this resource.