This is a *really* good deal on a HDTV tuner for your PC. The QAM version adds the ability to tune UNENCRYPTED digital cable channels. Since 90% of all D-CATV is encrypted, the QAM version is only necessary for those who cannot receive over-the-air HD signals. If anything, you'll likely only get the HD channels you'd be receiving via an antanna. Don't get me wrong - the ability to receive QAM is great, but for $120, this is AFAIK the cheapest any HD-capable tuner has ever been.
One thing to note: this card does not have an integrated MPEG2 decoder chip; instead, it relies on a DXVA accelerated software decoder. This works fine on most "modern" PCs and graphics cards (i.e. ATI RADEON-class, and its competitors), but you can download a
test program to try-before-you-buy.
Copperbox is a well-known retailer on some of the HD PC boards, such as the AVS Forum. Though their return/repair policy is slightly harsh, they typically get good reviews.