A coworker, who knows I am an HDTV know-it-all, asked me whether he should get a tuner card for his desktop PC or buy an ATSC tuner box for use with his new 1080p LCD monitor. He wasn't going to build or buy a specialized media PC, and in the beginning he just wanted to watch TV with no DVR functionality. Nor does he want to pay for cable or satellite. I immediately told him to buy a standalone receiver, and recommended the Samsung SIR T-451 based on comments on the AVS Forum.
For many years, I did not own a TV, but I watched a lot of TV. In the days of Mac OS 7, 8 and 9 I used my desktop Mac (first a Performa 6214 and then a PowerMac 7600) to watch cable TV via a tuner card. It became tiresome waiting for my "TV" to boot, or worse reboot. Plus, it was noisy. Then I bought a NTSC tuner box sold by ViewSonic to which I could hook to my TiVo, my DVD player, my computer, and analog cable; this was quite a step up as I could still use my VGA monitor, but I didn't have to boot my TV.
When it looked like the dreaded broadcast flag was going into affect, I bought a pcHDTV card for my Dell, and started playing around with MythTV and was hooked on the quality. Then I bought an LCD HDTV ready TV, and hooked my MythTV computer to it, and it was good. But it was noisy; and in exchange for perhaps an hour a night of watched HDTV programming, my TV room was noisy 24/7 with the sound of cooling fans. Thus the banishment of the MythTV computer to the basement. The upstairs TV gets its HDTV programming via a Dish Network receiver, and my TV room is blessedly quiet.
The same thing with the digital TV I threw together for the bedroom using an LG HDTV receiver. It's quiet, boots in seconds, and doesn't drain my electrical bill while off.
There is a place for media PCs in the entertainment center, but they should be quiet, specialized PCs (or of course iMacs or Mac Minis), not cheap, noisy, general purpose boxes. If you aren't in a position to shell out the big bucks for a new PC, a standalone OTA receiver is a good value and a good match for the "HD Ready" TV.