Wireless sensor network library suggestions

I've been playing at setting up a network of Arduino Pro Minis connected to various sensors and communicating with a central Arduino via NRF24L01+ wireless interfaces. Rather than roll my own protocol and library, it seemed to make sense to explore the existing options. Unfortunately, I'm not finding much other than MQTT-SN and some have given it a scathing review. (Although MQTT looks decent.)

Are there any other wireless sensor network libraries out there? Are my worries about MQTT-SN groundless?

Using a nice wireless library like RadioHead or RF24, it looks like implementing a subscriber-publisher-broker protocol would be fairly straight-forward, but if it's already done, why?