A quick search suggests that most headphones and hearing aids don't support it yet. This will be your greatest problem - nobody can use it. This seems like the future though so you should probably install it in your venue and get a few headphones that do support it to test it and to borrow to those who need help.

That few support it implies that there are likely going to be implementation/interoperability bugs for a few more years at least - nobody knows how bad these will be. Maybe things will just work, but growing pains should not be a surprise.

They claim latencies as low as 40ms - this is unacceptably long for a lot of music applications. For listening to the sermon at church good enough, but people may noticed if you are singing along. I'm not sure if this will be an issue, but it is something to consider. You might need a different system though.

It's a chicken-and-egg thing. Not many devices have it, so not many venues install it. Not many venues have it (perhaps because they've invested in other systems), and there's no pressure to change until there are many people wanting to use it.