I have two HTPCs and have invested about $800 each and several media boxes ($100 each) for light use TVs plus an iPhone and several laptops. I have 45 terrestrial channels, hundreds of satellite channels provided by PCI cards and sample network enabled satellite STBs, Netflix, Hulu, Pandora, Amazon streaming and access to any media files on the connected devices. I have not had cable or subscription satellite services for 3 years. The hardware was paid for in less than a year with the savings of not having a large cable or satellite package subscription and my monthly bill is usually around $70 including the broadband connection.
I agree that HTPCs are currently the best option for integrating ALL terrestrial, internet and satellite delivered media. Linear broadcasting delivery of video based entertainment will become niche market in the near future, just as linear audio broadcasting has transitioned in the past few years. The HTPC is the backbone of the home network sharing solution and it is available today!
I see STB units as not only stand alone devices, but also as feeders for the integrated home network. I look forward to the day where OTT widgets aren't really Over The TOP, but rather just standard business!