He's saying that his car is accelerating slower now than when he first got it and when he releases the gas it is decelerating quicker than then as if something was holding his car back. He's asking if anyone else has experienced this before and if it is normal for his car. I thought the same thing too, but after 4000 miles and the car broke in it seemed fine. Maybe it's something the car does when it is breaking in. Either that or it was all in my head (Which I think is what happend) it'll go away, you're probably just thinking too much.
If it is much more serious than that, it could be that the rear brakes aren't calibrated correctly, In that case I would contact the dealer.