Obviously, if you have a Plume WiFi set-up you need HomePass, and if you don't, you don't. That said, I'm giving my thoughts here in the hopes they may be useful to someone considering Plume.
Generally HomePass works well, is clearly laid out, and other than a few odd choices is intuitive enough. It does not feel like a native iOS app though, and the navigation stack seems quirky if you're expecting the usual iOS drill-down approach. There is no iPad app (guys, HomePass is being used for heavy lifting, throw us a bone here), so you're going to be stuck doing all your network tweaking on your phone. Fortunately for most users, heavy tweaking should not be required.
It's a shame there's no way to set the icons for devices: I have a HomeKit switch that shows up as a laptop, and I cannot change that. Also, while Plume grabs ZeroConf (Bonjour) names from devices so most devices on your network will be nicely named in the devices list, HomeKit devices show up with little to no differentiation. It'd be nice if HomePass could be updated to mine the HomeKit catalog for device names.