Took the new 350 Coupe from Texas to California, 1300 miles. I thought I'd share a couple observations. First, it's a great road trip car; comfortable, resonable milage, fast and smooth. The cruise control is the best I've ever used. Easy to operate, and exceptionally smooth and undetectable when operating.
On the negative, the dynamic handling package (Agility Control) has some real drawbacks. The stock "E" ride is a little wallowy, and particularly noticeable going faster, or in high winds at speed (85 and up), or curvy roads. Push the "S" button for sport suspension, and the ride is perfect, still comfortable, but much more controlable, and planted. No issues at even higher speeds. However, in "S", the car stays in 6th gear, killing mileage. You can get into 7th gear in "E", then switch over to "S", and it will stay in 7th only until the speed drops to about 70, or if you use the gas a little heavier to pass or something. Then it goes back down to 6th, and stays there. No amount of accelerating and lifting will make it shift up to 7th. The only way to get the mileage benefits of 7th gear, and the "S" suspension is to go into manual shifting while in "S" mode, and shift manually to 7th, only downshifting when needed. I'm really not very happy about this issue, it seems the trans should be able to have crisper response etc. in "S" but still utlitmately go into 7th on its own.
As for mileage, the car only had 1200 miles on it at the start, but at 85+mph, in very heavy wind, I got 25-27 mpg. The next day, without the winds, and driving 80-85 mph, I got right at 30 mpg. I imagine the number would be much higher driving as low as 70.
I'd be interested in other people's thoughts on the car's performance on long trips.

 

I drive between Champaign, IL and Chicago about twice a month in my C350 coupe. Its a 150 mile drive one way. I normally average about 34 MPG with cruise control on at 70-75 mph with just myself in the car. Right now it's got about ~8000 miles on to odometer, had the car since October.