Over the weekend, I hooked up my HTPC with a USB cable tuner and antenna. Without a CableCARD (and who wants to deal with that hassle?) the cable tuner was only able to access the analog cable channels. Since US broadcast television went digital in 2009, over-the-air signals are actually better quality (for me, anyway). I get ABC and Fox in HDTV, and about 15 other channels in standard def.
Now running Windows Media Center (which is pretty awesome, btw) on a Windows 7 box hooked up to the TV via HDMI, I can play movies, tv shows and music from my pre-existing libraries, throw up a picture slideshow, play and record live TV via terrestrial broadcast, use Apple's Airplay from my iPhone or iPad, and access Netflix and Hulu for internet TV content. All controlled by a single remote control.
As I'm not actually paying for cable myself (corporate perks!) I'll still use cable to get my Mythbuster's fix. But the next time I move, I suspect I'll forgo cable TV entirely.