The controller needs to be running in order for the neighbor scanning and fast roaming functionality to work, as well as for statistics gathering from your devices.So for the Ubiquiti stuff, out of sheer curiosity, does the Unifi Controller software need to actually be running 24/7 for the APs to work? Or can you just configure them and leave them to run on their own? I'm finding it difficult to justify an extra $175 to $200 for a "Cloud Key" device. Ideally I could set them and forget them.
I agree the Cloud Key is steep if you're just using Ubiquiti for APs. If you have another system, you can run the desktop version of the UniFi controller (which is just a gross wrapper around a Java server with some crappy database backend so you get to be spammed with Your Java Is Out Of Date alerts all the effing time) which is free.
I only use UniFi for switching and this is what I do.
WARNING: I hope you're not planning to wirelessly mesh with Ubiquiti... Their APs all use a single band shared mesh backhaul + client serving architecture, which is the worst performance for wireless backhaul.