Well, I'm closing in on 1,000 miles now and am on my third tank of gas. My early impressions of the car are:
Pros -
Styling is great, but then this is very subjective. Interior room is great for this size (exterior-wise) car. Power is great for a 4 cylinder. Braking is impressive and I like having disks on all four corners. Quietness for a car of this price. Controls are pretty good and easy to find, although I dislike the dimmer switch that must be pushed forward and pulled back. I much prefer the toggle style dimmers in my American cars. Sound system is pretty good. Assembly quality seems very good. The car handles well and the Michelin tires perform great in snow. The steering is a little too light with too little feedback, but not a major problem.
Cons -
Heater doesn't distribute heat well to the footwells. Windows fog up with more than two people in the car. The seat belts are too close to the interior panel making it hard for me to grab ahold of them to put them on. The receptacle is also too close to the console leaving insufficient room for my hand to insert the buckle. The electronic throttle is too light (too little feedback) making it hard to make a smooth start in 1st gear as the engine is also too quiet to hear. In an automatic this wouldn't be an issue. The storage bins are all the wrong size for common items. I use a 4x6" spiral bound notebook to keep my vehicle log for fuel purchases and maintenance. The cubby under the heater controls is about 5 7/8" wide which means this notebook won't fit in it. It fits perfectly in a similar cubby in my Chrysler minivan. Likewise, the top compartment of the console looks like it was designed to hold a short stack of CDs, but again it is about 1/8" too small for a standard CD case. And the bottom compartment looks like it is the right size for a standard square box of tissues, but again it is about 1/8" too small. Fortunately, the tissue boxes give and I can jamb one in there.
Neutral -
Fuel economy - First tank was 27 MPG (60-70% highway probably) and second tank was 29 MPG (maybe 70-80% highway), both in weather running in the high 20s to low 30s. I'm hoping for at least 30 in my normal mix of driving once the car is broke in and the weather gets a little warmer. I drive 70-80% highway typically. I'd like to get closer to the 34 highway rating, but I doubt that will happen as all of the road tests I've seen of Hyundais show that they don't get as close to the EPA ratings as to most other car makers (Toyota in particular does well in this regard).
I'm be curious to hear others initial impressions of their Sonatas.
Matt