Yes Jack is right, another massive advantage is that with PJDL devices can arbitrarily transmit data safely, enabling new ways of building things, for example sensors and actuators can communicate directly with each other without a master in the middle.
I use PJON in combination with MYSENSORS in my smart home system. It is the first wired protocol that works so stable and don't even need extra hardware - just one free IO pin. I have over 200 smart sensors and devices around my house. PJON was a perfect solution for all problems I was facing with wired and wireless communication for DIY smart home solutions. With some luck PJON will be officially supported by MySensors already from next release - beta test are already done. I think this will make PJON more common.