There was a lot of critique about this on the Tesla forums when the car first came out. I think this is a legitimate criticism. Particularly with Android phones having such difficulty; many people had to resort to toggling bluetooth on and off as they approached the car to make it work. This was never an issue with iOS, but there's obviously a huge
potential for an issue (buggy software update with unintended consequences, either on the iOS/Android or Tesla side).
Our issues were limited to 2 instances:
1. When the car was delivered, it took them about a week to add the car to our Tesla/app account (which is the only way you can pair the car to the phone's bluetooth; once it's paired there is no app required), which meant we had to use the backup RFID keycards, which is more of a pain than it sounds like. Yes, you COULD carry it like a fob, but it's light and thin and could much more easily get lost (on day 1 I dropped it out of my running shorts onto the floor at a coffee shop). So you put it in your wallet, which means it's a 2-hand process to retrieve the card to unlock your car. You also have to remember to tap it to the car to lock as you walk away.
2. My wife's phone died on her once, so she had to pop in to a wine bar for a quick top-off. Of course most places happen to have iPhone chargers, but you can't count on them having all the phone power connenectors you might need; lightning, micro-usb, usb-c... etc. Particularly in the middle of nowhere. Yes, she could have called me or Tesla roadside... if her phone worked! Using the app I can remotely unlock the car for her, but i'm not sure how long this unlock 'lasts' for, and whether i need to do it again to enable the car to actually drive. Again, this is difficult to coordinate if she's a 5 minute walk away from the car (for instance).
There are, however, benefits vs an RFID fob, and I'm massively in the latter camp. Having lived with it for a year, it feels like all upside and no downside.
The obvious is that I don't need to carry a separate fob. Every time I walk up to the car, I just get in and go. No buttons. Nothing extra I need to carry. When I move our other cars around, I have to always remember (and usually go back inside) to retrieve keys.
My wife and I share the car, and we commute together. We can easily swap seats; I get out at my dropoff location for work, she hops behind the wheel and drives off. No "who has the key" or "do you also have your keys, or do you need to borrow mine?" We frequently go for runs after work. You never have to think about having 2 sets of keys, or handing the keys to the next person to get back to the car. If I finish my run before her, or want to retrieve something from the car, I know I can just get in, no question.
The car sits in the driveway. I don't even carry house keys. If I'm out for a walk, I pop the door, and press a button on the touchscreen and the garage door opens, and I walk into the house.
It's just so insanely convenient and works so well.
When people were complaining about Android functionality, there was a lot of talk about fobs. Then Tesla said they'd hand out free fobs to anyone who asked. I originally thought I'd want one, but I haven't even thought about asking for it.