Some other lessons learned ...
TrueCar is pretty much all or nothing - i.e. you can use TrueCar and get the price from the dealer. You can then negotiate and try to get that price or better than that price, but you can't do both.
For example, my price through True car was around $14,500. I think I could have negotiated hard and maybe gotten $14,200 or so, but I would have not wanted to mention TrueCar to do that - and maybe not then, TC includes the $600 doc fee, so the actual price would have been around $13,900. (But you can't walk in and say "I contacted you through TrueCar and they said $14,500, but I want to pay $300 less than that."
Truecar gives you prices from three dealers - it almost always makes sense to take the lowest TrueCar estimate, unless there is some outside reason not to (lowest price is 75 miles away, Dealer B is $100 more but has lifetime oil changes, etc.).
But you don't always get the SAME three dealers - for example, I got quotes from three dealers. Then I went into the dealer and they needed the certificates, so they had me do a new request - which had one of the previous dealers (not them) and two new ones. If I had requested certificates twice before-hand, I would have had 5 dealers to choose from (wouldn't have changed my deal or choice, but ...)
You have to somewhat play with the options a bit ...
When I went into TrueCar, I requested the popular package with floor mats - which was around $14,450 on TrueCar. The car I actually got was around $14,700, but had $220 in options - floor mats, cargo tray, cargo net, and rear seat cupholders. Hint - either find a car on the lot and jot down the options, or many dealers will have a copy of the window sticker uploaded. Put those options in TrueCar and you will be closer to the final price.
Finally - I learned a bit from a co-worker's experience. The dealer I went with had the lowest price on TrueCar, but was about $1000 higher than the TrueCar price on their own website. Another dealer was around $300 higher than the TrueCar price on the dealer's website and $600 less than the dealer I went with. However - when I looked at the cars on the dealers lot, most of them had window tint, most of them had paint sealant, most of them had pin-striping, most of them had N2 tires, most of them had lock lugs on the hubcaps. There wasn't an additional sticker for those items. What that usually means is they will price the car $1000 more than the advertised price, and with work, you can buy it for the price they initially said. If you want window tint, etc, it isn't a bad idea, but otherwise it can be.