What parts and service were you waiting for?
Short question, requiring a long answer.
My main battery was found to be defective when my 2015 P90D was a few months old. They refused to simply give me a replacement despite the car being so new, saying that was not how Tesla did it, instead they would remanufacture my battery. So they installed a loaner 85KW, but instead of taking the estimated 4 - 6 weeks as they said "it depends on how backed up the remanufacturing process is", it was 6 months. When they re-installed my battery they ran diagnostics and found that the battery was defective, wouldn't hold a charge. I was livid -- how could they have shipped the battery without first running diagnostics? This time I insisted I get a new battery, else I was going to fly to Fremont. The people at the SC were great -- truly my advocates -- but they had to fight management at Fremont. They won, and a new battery was shipped.
I was dubious as to whether they were truly giving me a new battery, but it turns out they did. How did I know? Because between the time my car was built and then, they had changed the design of the battery and to put a new style battery into my car required an adapter kit, which hadn't been sent, so that took a couple of extra days to locate and be shipped in.
Then, I made the mistake of running the nose of the car over a parking curb. Because of the frunk, they pack a whole bunch of stuff down very low to the ground, which got destroyed to a bill of over $6,000.00. The authorized Tesla shop told me it could take Tesla 4 - 6 weeks to get the parts shipped, because they were so slow in delivering things. In fact it was 10 weeks and not everything showed up, so the shop borrowed the missing parts off another brand new Model S that was in the shop waiting for its parts to arrive.
Then the drivers door handled failed. The new handle took over a week to arrive. When I was picking my car up, the fellow said "Your car was one of 5 that we replaced door handles on today." He didn't need to tell me that.
Then the airbag warning light came on, and they said to get the car to them immediately. When I dropped the car off they said that when that light comes on, the entire airbag system is inoperable. They determined that the wiring harness had failed, and they ordered a replacement which arrived in under a week, however there was a problem. The harness that arrived had the correct part number, but wasn't the right component and would not work on my car. Tesla had apparently designed a brand new harness, but gave it the old part number. That took weeks for them to figure out.
This was in the second half of December with cold weather in Philadelphia, when the car was a little over 2 years old. While I was driving the loaner car I realized that the heated seats which were really not perceptible in my car were really warm in the loaner car. They checked my car and found that the bottom seat cushion of the drivers seat was defective. And, instead of having to simply install just a new heating element, or the seat bottom as a unit, they had to replace the entire drivers seat. When I asked how much that would cost if it wasn't under warranty, The young gal cheerily said "I don't know **all the ones ** we've replaced have been under warranty". They said it would take 4 to 6 weeks for the replacement seat to show up. That was the first week of January. When I decided to write the big check and pay off my lease 6 months early it was the second half of April -- 3 months later -- and the seat still hadn't arrived. I suspect that the reason why is that my car had a gray interior and they had stopped making gray ones about 12 - 18 months earlier. I hope that whoever buys my car lives in Arizona.
The only saving grace was that there was a large service center about 20 minutes from my home, which really helped given all the many trips I had to make there.
Moral of the story? If you never have a problem with your Tesla, you are fine. However if you do have a problem, God help you.