I've used the app successfully once, inflight to rebook an itin for irrops that I couldn't manually do myself. A couple of other times it was useless and a waste of time. The time it did work it took me a few hours of back-and-forth with the agent, or multiple agents. Only reason I stuck with it was because I had plenty of time in the air FRA-ORD.

I don't like how if you toggle to another app, your screen times out and goes black etc it forces a re-connect which can be lengthy. Sometimes the function crashes altogether. While I see merit in having this functionality its generally more frustrating than its worth IMHO.

Also, some people may not know but the Marriott app also works inflight on the plain unitedwifi connection.