There is an extensive discussion of UHF antennas on www.avsforum.com; I think, without verifying, that the antenna gurus consider the Terk to be a waste of money. My recollection was that the now discontinued (but still occasionally available) RS bowtie was considered the best, esp. if you hardwired in a 75 ohm to 300 ohm transformer right at the terminals and used shielded cable back to your HDTV box.
If you are in the DC area and want a free UHF directional, there's a new one in my garage taking up space...
Also, since the UHFs are directional, check www.antennaweb.org (I'm doing this from memory). Gives you, for a set of input coordinates, all directions and distances to the digital HDTV broadcasts in your area. Can be useful for initial set up.