A little update: my church recently upgraded to a 32-channel Presonus AI, in order to accommodate the growing number of people we have on stage.
This has increased the number of iDevices in use, as most of us are running Qmix for IEM control on our 'phones, and OnSong separately on iPads, for charting. There are also multiple Apple TV's for the various projection screens, additional iPads for FOH control and projecting song lyrics, and most recently, a Line 6 wireless headset for the pastor.
We haven't experienced any dropout issues with the Line 6, but it has worsened the problems we were already experiencing with wi-fi connectivity for Onsong and Qmix/SL Remote.
We had 18 wi-fi devices going last Sunday morning, just for the music program, and Qmix AI was up and down like a toilet seat.
Our tech dweebs are currently looking at rebalancing our network across the 2.4 and 5GHz bands, but it's looking like we may have to go all the way to zoned wi-fi in order to get the stability we need.
All of this has made me quite pleased with my decision to go with the Shure PGXD system, which operates outside the wi-fi band, at 900MHz. My radio doesn't add any grief for the tech crew, sounds just as good, and has been just as reliable as any instrument wireless that operates in the wi-fi band.
I realize that this doesn't necessarily translate to what you'd experience in a typical club or dive bar, but it's definitely the way installed audio seems to be headed, not just in churches, but in live theatre as well.