Anyone else amused the second screenshot in that article exposes junk along the top edge, junk that is hidden when overscan is applied, as is the intent for broadcast TV? The author may use "professional monitors", but most people don't, and most people will find disabling overscan to cause "network tickers and logos" to NOT be in "their usual places", talking heads to be shrunken, etc, and some content to display junk along the top edge or sides. My local NBC HD channel doesn't fill the whole frame at the top for any HD program, leaving a 10-15 pixel tall black bar along the top, with a visible bright white pixel at the upper left, which is actually contained in a row of about 10 grayscale pixels. It's been that way for years, and it's the main reason I ended my experiment with "Television" mode after just a couple of hours.
For these reasons, I think it's misguided to disable overscan for broadcast TV, though obviously only one device should be applying it, either the TV or the PC. You're not going to lose any valuable information by leaving it on, because broadcast TV is meant to be overscanned, and I'm skeptical there is any real sharpness improvement that can be consistently observed under normal conditions by disabling it. So I don't see any advantage to disabling it. I recommend putting the flat panel TV in full pixel mode (1:1 mapping) and setting WMC to Flat Panel, letting WMC overscan broadcast TV. Apparently this doesn't affect how WMC displays DVDs, MP4 files, and presumably other HD files you can play with the the help of codec packs, but I've only verified it for the native MP4 support using the AVS709HD test pattern. That said, I use XBMC for non-broadcast TV video, and my MKVs and whatnot are not overscanned, which of course is what I want for them. It's just broadcast TV that needs it.