I unplugged the D-Link DWL-122 (802.11b) adapter, plugged in the TiVo-branded g adapter, and it Just WorkedTM. Better still, it's 802.11g and it gets significantly higher signal quality (82% whereas the DWL-122 got signal varying between 60 and 70% and only that by hanging it out the front of the entertainment center--the TiVo-branded one is fully inside the entertainment center).
So, I'd give it 2 thumbs up (or, hm, since we're talking TiVo, not movie reviews, perhaps 3 thumbs up).