Not all have it but it does happen. How bad it is, is subjective. For some even a minor vibration could be an issue and vice versa. Mine has it but I'd still buy the car again even with it.
Keep in mind that for most that have it, it is a
very narrow speed range if you have the 38-42 mph one. I've never experienced the 80+ mph one so can't comment. I know someone with a brand new MS LR who is obviously concerned but hasn't had any issues yet. It was just delivered.
Don't know if Tesla will ever fix it. I did find that the track pack brakes made mine even less of an issue so there is a good excuse for the wife if you buy one and have some vibes to buy the track brakes.
No guarantee it will be better but so I was the first to report the difference and someone else just noticed it as well.
Even if my vibes were worse at about 40 mph I spend so little of my time at that speed that it is non-issue for me. I typically transition it very quickly anyway. As with all things YMMV.
This is one of the few cars I've owned that it something happened to it I'd immediately rush out and buy another one, known warts and all. I fixed the 21" tire wear issue for $200. The 21's look best on the car but I bought 20" for my track pack brakes and never heard of the tire wear issue with the 20's not to mention the fix will help the 20's anyway.
I've tested the top speed limiter with the brakes and no vibes all the way up. On anything more than
very very mild acceleration, or maintaining the speed where the vibes are at (about 40 mph for me), I never am aware of them. As I wrote earlier, If I hadn't read about it, I wouldn't even think about it. It now falls into what has been seen can't be unseen for me. I'll always be looking for it now though I almost never ever do now.
If really concerned about it, buy used and drive it beforehand.