For me at this point the fob and mobile key perform about the same, and neither is good. I'd agree that they work as expected at most about 1/4 times. The range is not good for either, which also doesn't help. I was leaving a store with my girlfriend who drove separately, it had started pouring while we were inside. She unlocked her car from inside the store (with a standard fob) and ran. No problems. My fob was out of range, my app wouldn't wake the car remotely, so I just ran. Phone in one hand and unlocked, groceries in the other hand. The car took 3-5 seconds to wake up and unlock after I got to it and pressed the door handle (despite proximity unlock being on), leaving me much wetter than necessary. This is unfortunately the rule rather than the exception for me, just not always in heavy rain.
On top of that, I do use my valet card to lock/unlock the car somewhat regularly. That has even worse performance. I stand there sliding it around, taking it away, putting it back, over and over with nothing happening. It almost always takes 5 tries or so, while people look on wondering what poor decisions I've made with my life. I keep meaning to ask the service team about this, because no one I've asked has used it enough to say if this is "normal" or if I have a particularly broken NFC reader in my car.
I don't normally like to post this kind of complaining here, but for issues like this I always have a hard time judging whether those of you who say "it's all fine" are just more patient, or if I actually have something I need to press to get fixed.