Having mostly driven manual cars, i decided to go for a new Automatic IS 200 SE, and i can honestly say i would never go back to a manual. The sheer effortless drive, the lack of any noticeable gear changes, and the general smoothness have convinced me that auto is the way to go.
The auto is slower off the light, but when using the 'ECT power' button on the auto gearbox, i don't think there is any noticeable difference in acceleration once you are moving.
As mentioned above, drive both and see which suits you.
Good luck