I bought one a few weeks ago & it has fixed a problem or two.
When watching some SD OTA programs with WMC7 there was some stutter, and sometimes a couple times per minute & seemed to be caused by the 29/59 bug. The 6450 fixed this. However I never noticed this with HD OTA.
When watching HD OTA using MPC-HC the frame rate would be one rate for about 16 seconds & then another rate for about 5 seconds & kept repeating. And the graph's Green video line would decrease & also indicate this. With the 6450 the rate stays constant & the Green line stays flat. So it fixed a problem even though I never noticed this when watching HD OTA.
So I thought it was worth $15. The card does have a fan but I don't hear it because the HTPC is hidden in the corner, & I think the PSU's fan might be louder.