I don't think OLCI is useful at all. BUT, the Chat feature is useful if the front desk actually bothers to look at it. Most of the time they do, but occasionally I've had them not answer.

If I'm getting in after 10pm local time, I'll send a message via Chat to let them know.

Do hotels still even do Mobile Key? It's been ages (years) since I've seen it actually show up in the app and work, even in new-build hotels.