Gadgetaholic reviews the AVerMedia AVerTV Hybrid Ultra USB HDTV Tuner.

Quote from the review:
"So how well does it perform? I can honestly say it performs really well. The HDTV reception is clear using the powered HDTV antenna I bought especially for the unit.
There was some pixelation on some channels but that's probably because of the reception and not the hardware. WMC responds very well to heavy channel surfing; there was no detectable delay. The tuner hardware does a great job of decoding the signals internally to reduce the load on the CPU. "
Read the full review on Gadgetaholic.