Let me start off by saying that I absolutely love my P85+, I also own stock in Tesla and believe they are going to change the direction most other auto makers are going.
That said, I did have an issue on 10/9/13 where my car would pull to the left under acceleration and then back right when I laid off the go pedal. I purchased the car 6/22/13 and it had 4,400 miles on it the day I felt this problem. I am very mechanical having worked on cars my whole life. Before I put the car on my lift, I researched online about the MS pulling under acceleration. After weeding through usual online chatter, I did find posts from a few people who said some suspension bolts had loosened up in their cars and the service center re-torqued and loctited them. When I got home from work I put the car up on the lift and couldn't believe what I found. The passenger lower ball joint nut was not just loose, it was a few threads away from falling off! (I have pictures, but don't know how to post on here) I couldn't believe it, since in the 30+ years I've been working on cars, I've never seen a ball joint nut come loose. It simply just doesn't happen. I decided to check all the bolts in all for corners of the car and found the same nut on the drive side to be hand tight (it was loose, but hadn't spun all the way down yet). I also found a loose bolt on an alignment arm on the driver rear. Had I not noticed this "pulling", which by the way my wife didn't, I probably would have had a day before the passenger ball joint came completely out and my passenger wheel would have been parallel to the ground. The potential for loss of life and/or vehicle damage was huge!
My larger concern than my own car which I fixed, was that Tesla knew about this and didn't do anything proactive to stop it. Again, it was only internet postings, but to see that other people said they had the same issue is scary. These types of bolts/nuts are never supposed to loosen up in any car and for it to happen to multiple vehicles crazy. I wrote Tesla on 10/10/13 and I received a call the following day from a gentleman from the Long Island City service center, where I originally picked up my car. Omar went over all the details with me, offered to repair my car, and told me he was aware of the importance and would escalate this to the proper people immediately. Unfortunately I have heard nothing since, which seems very un-Tesla like and disappointing.
I urge any of you that start to feel your car pull one way or the other to have someone qualified look at it and make sure that the hardware on all 4 wheels are tight. To me, besides seeing the car actually turning left under acceleration, if felt like the rear of the car sort of squished right. That's just my way of describing the sensation felt when the nuts were loose.
Once more, I've owned many cars and have to say, so far the Tesla Model S is my favorite. I cannot say enough great things about the MS to anyone that inquires. I am concerned that after my discovery and disclosure to Tesla there was no follow up and I fear others will have this same issue. Hopefully this posting can help prevent a bad situation.