OK, so I don't drive much. I work from home, so I do mostly short trips with an occasional 30 mile highway drive. That said, I love my S40. Great pickup on the highway when I need it (80 without even trying), OK gas mileage around town. I have the premium sound and moonroof. Loved the moonroof before we hit rainy season here in Miami, and the sound system is like being in a concert hall. Not many S40s on the road here, so it's nice having a somehwat unique car. Extremely pleased so far (even though I haven't even broken 1,000 miles yet).
Pickup, highway acceleration, sound system, moonroof, split rear seats, and that cool center console
Rear visibility ... I get nervous every time I have to change lanes on the highway.