Linear regulators in Arduino get hot. I have made some Atmel/Arduino boards with switching regulator. I can take hundreds of milliamps from it and it wont get hot even though I use 24V input.
Of course this is no secret, so a model with a switching regulator could be usefull for those who build larger systems and do not design their own PCBs.
This is one example, and there are others. They are a bit like old 7805 devices.