Got the Knocking Live update last night as well. Used it over 3G with the wife's 3GS and son's 3G (my old one). In the Dallas area we've got strong 3G mostly so our connections were pretty decent with audio. Can't say how it'll work with other locations.
But for the price of FREE (as in beer) and works with 3G, 3GS, 4 (both cameras) and over 3g, its pretty hard to beat.