I find it easier/faster to just stick the card key in a spare credit card slot in my wallet and hold up the wallet to the lock to open it.
Long as there's no other RFID cards in there, no problems seen and don't need to hunt your pockets for the card.

Do you stay at any specific properties regularly? What type of phone do you have?

Am curious as I have issues constantly.

I normally use it when it is available. I like skipping the front desk when I initially arrive at a hotel. I also pick up a plastic key at some point when there is no line and keep it in my wallet as a back up.

Never used it, and probably never will.

I usually store my keycard in my phone case (there's a small flap in the cover that can fit 1-2 cards) since taking a keycard out of my wallet can get annoying when you're running around the hotel and I tend to drop them when they are loose in my pocket.

I simply tap my phone to open the door lock and elevator. Doesn't matter if my bluetooth is on, Bonvoy app works, phone is unlocked, or even if my phone is still alive after a long day :) I also prefer this because I won't leave my room without my phone, whereas I may leave without my wallet.

I've never used at Marriott. It's rarely offered and I don't really trust Marriott IT. Have used Hilton's a few times, and would use it again. Hilton has a better app. I especially like the ability to select rooms from a map.

It has never worked for me. I don't even bother trying anymore.

What process? If you do online check in, you just walk up to the desk, hand them your ID, and they hand you a packet with the room keys. It takes less than a minute. Occasionally they ask you if you'd like an upgraded room. For "check out", you either do it in the app, or just leave.

Now, if you don't check in online, have special requests, or want a paper copy of your bill, those are all processes. But the mobile key doesn't help with those.

That said, other than shaving a few seconds off the check in process, I don't find online check in that helpful either. As others have said, if you could select your room like in the Hilton app, it would make a lot more sense.

exactly. This scares me too much. Good old room key is better :)

As others have noted, it's not terribly reliable...IF it's supported. I've only had it work once, and even then it only worked for the first day of the stay. After that the app would show that I'm staying at the hotel, but never gave the option for mobile key.

Overall, other than trying to speed checking in and getting to my room (especially after a long flight), I don't see it as being all that great of a benefit.