One thing that really stood out for me about the Genesis is its (almost too) firm ride. I did not get a chance to drive the V6 with the 17" wheels, but the 4.6 with the 18"s makes you feel every bump on the road, especially around town. Even at higher speeds, when rolling around on the wickedly rough parts of the LA freeways, the suspension does feel quite busy, but never unsettled or floaty. Certainly, the trade offs are good high-speed stability and being very flat through the corners, despite its 2-ton curb weight.
Test driving the Sonata 2.0T SE and the Genesis 4.6 made it clear that the Sonata clearly had the more comfortable ride and still seemed to handle as well because of its significantly lower weight. Obviously, Hyundai didn't want the Genesis to be soft and floaty like a Lexus ES350 or a Cadillac DTS, but the TL and the G37 had noticeably more compliant suspension setups.
I'm still (relatively) young and willing/able to deal with a firmer ride, but because the Genesis LOOKS like a big, bulky luxury sedan, a la Lexus/Mercedes, the firm ride came as an even bigger surprise. Perhaps the V6 with the 17s ride a bit softer. Anyone in the market should certainly check it out and drive competing cars back-to-back.