There are many cars on the market today including the Toyota Prius range, Hybrid Camry and the new 11th generation Corolla, that have a transmission known as a CVT or Continuously Variable Transmission. This kind of transmission does not have the tradational gears that a normal automatic transmission.
A CVT instead has an infinite number of gear ratios available and of course the transmission will make continuous and seamless adjustments depending on what the drivers needs at the time.
These kind of transmissions are a highly efficient delivery system that does ensure power is not wasted between up and down shifts, and also can deliver excellent performance, it can also help in create a more smooth and comfortable drive.
Of course this kind of drivetrain does remove the need for gear changes which elimates the jerks or pauses that can be noticable in acceleration in many tradional automatic gearboxes.
Which does mean that in a CVT when you put the foot down the transmission will produce a smooth, and highly responsive, response in acceleration.