However, while the Uno is a helpful board for your beginner ... It's like a shrunken version of the Arduino Leonardo as it features the same ATmega32U4 microcontroller, micro-USB port, and pinouts.

The newly released Arduino Leonardo has a few very interesting features, most notably the ability to act as a USB keyboard and mouse thanks to the new ATmega 32U4 microcontroller. This feature ...

It’s a significant update. The Arduino UNO and Arduino Mega 2560 update the Duemilanove and Mega respectively. They now use an ATMega8U2 instead of an FTDI USB to serial converter chip.