The virtual qwerty keyboard on apple's iphone allows user to enter the as quickly as they would on another handset's physical keyboard, but they'll make more mistakes in the process

The Chicago company User Centric's has conducted a usability study comparing the iphone qwerty keyboard to other full keyboards currently out on the market. The test included typing text messages with plain text not using any auto text features.

You can read User Centrics write up on its website