Well we pulled the trigger and I was pretty happy. It turned out that the savings from Costco vs other places was enough to more than pay for the membership (and we did the executive membership - not that I think we will buy enough to make it worth it, but because if we dont, they will refund the difference).
So I went online and ordered the tires. I had called three costcos and they all seemed to give a different story on different days whether they had them in stock or not, if they could hold stock tires for me, if they could order them for me, etc.
If I could have done a no-cost order the tire to the store or hold it for me, we probably would have gone to delaware and done it tax-free. My only downside (still ahead financially though) is that I ended up paying tax on the transaction.
So I bought the tires credit card on the 18th, right before dinner at about 6pm, from a hotel room outside of Quantico, VA (had joined the costco at that location earlier in the day). The tires were delivered to the Costco of my choosing in NJ, and were ready to be installed Friday PM.
We got to costco, and decided we would eat a pizza there for dinner and then shop. We got there and there was one person dropping off their car. When the guy got to us, he said there were two cars in front, so figure 1.5-2 hours. Seemed like a long time, but thats why we planned how we did. This was at around 6pm Friday evening.
The car had two different TPMS part numbers, the tech was very thorough. They had ours in stock so they proceeded with the service. Took about the whole 2 hours. Seems like they did a thorough job, and mentioned coming back in 25 miles for a torque check-up. He said he had to spend some time cleaning corrosion on one TPMS, so it seems that he was careful.
We are SUPER happy with the tires, and quite satisfied with Costco.