I have last year's Sony 42 inch (the KDF 42WE655) and your dad was probably looking at the KF42 WE610, which is the new model. It's an awesome picture on both over-the-air HD broadcasts and with semi-decent DVD player.
The TV itself is not as large as you would think (maybe 42 inches total, across). I have mine on a dresser in the bedroom (the short side of 14x17) and, if anything it's almost a size too small. If this is his primary TV in the house, a 50 inch may be a better choice. You have to be closer than 6 feet to the TV to see any kind of screen-door effect.
Cable hook-up is always iffy, but he can use the cable-card slot if he's not big on pay-per-view.
If he does use a cable card, that still leaves his over-the-air antenna free to pick up the 12 to 18 HD channels broadcasting in your local area. A week of Nature on PBS, football and baseball on Fox in high-definition, and he may decide cable is not really all that important. I certainly would not pay the cable company extra for the local channels, when they are probably free in high definition.
Given that the TV runs less than $ 1,600 here
http://www.onecall.com/ProductDetails.aspx?sHist=12-79,6-2&menu=true&id=28433
and probably even a little less than that if you go to shopping.com, it's a great buy and a much better overall value than the Aquos. The 50 inch runs about $ 1999 (about $ 450 cheaper than the local big-box store, assuming that sales tax balances out the shipping charges).