For many use cases, yeah, PXE is great. Classrooms/labs, digital signage, or anywhere you need distributed I/O, it makes total sense.

The biggest downside is your PXE server going down is going to kill all the Pis, so if you are doing something important you need a highly-available PXE setup. And if you have that, it's probably a better place to host a lot of the services people use Pis for in the first place.