The RasPiO® Pro HAT was developed out of the perceived need for a HAT which puts the Raspberry Pi's GPIO ports in numerical order and clearly labelled. You don't have to count pins or wonder which port you're connecting to.
Each port has a female socket to plug your wires or components into. The ports are arranged, along with plenty of power and GND sockets, around a 72-point breadboard.
If you want to do some electronics, it's made a lot easier for you. LEDs need no current-limiting resistors because they are already built-in.
Pro HAT also has a protection circuit on each GPIO port, which means you won't damage your Pi's ports by wiring something up incorrectly. (But it is still possible to cause damage by directly shorting 3V3 or 5V to GND.)
Additionally, if you want to bypass the 330 Ohm resistor on a GPIO port, you can connect directly to the unprotected side where all the ports* are broken out as through-holes. This is particularly useful for buzzers, which usually require slightly over the 10mA limit imposed by the resistors.
Ben Nuttall and Dave Jones have created GPIO Zero as the ideal way into Python GPIO programming. Using it with the Pro HAT means there is nothing to install before you can start playing.
Click here for more details and examples
*Apart from GPIO26, which is used for the HAT EEPROM