Very cool. Enjoy it!
10 day waiting period though? 
It was a combination of two things: the Bloomberg-financed initiatives 594 and 1639 in Washington state mandating that all sales and private transfers go through a FFL and that a background check be conducted for all transfers, amongst many other restrictions. For many years, if you held a Washington Concealed Pistol License, and you bought at a LGS, you had the phone NICS instant background check done at the point of sale, and could walk out with your new handgun. Private sales/transfers had no background check or paperwork requirement: you exchanged money and walked away with your new firearm. Effective 1 July 2019, the FBI decided they could no longer participate in the instant background check for the state, so it now falls to local law enforcement to do it and having a CPL means nothing in terms of the waiting period. State law gives them 10 business days to either clear or deny the transfer. The typical handgun transfer fee in this area is $ 25, although I have seen a range of $ 15 to $ 50.
For this purchase via Armslist, I went to the LGS, bought the pistol from the seller, we both filled out the sales/transfer paperwork, I filled out the 4473 and background check paperwork, paid a $ 27.19 transfer fee ($25 plus local sales tax) we shook hands and he drove away. The LGS now has to store the pistol in their safe and I have to drive back there in 10 days to pick it up. One trip to the seller and two trips to the buyer. So it is a real pain in the tuchis, and I have not heard of any significant upsurge in denied purchases as a result of the new requirements.
The same requirements now apply to the gun shows. I am a member of Washington Arms Collectors, which does a large show in Monroe or Puyallup every month. Since the change in state laws, the shows are now a ghost town. No one wants to drive 100 miles in Seattle-area traffic to go to the show, buy a handgun, and then have to make another long drive 10 days later to pick up the pistol from the FFL. The only ones making a profit at the shows now are the FFLs doing a transfer. If I am driving 85 miles to the Puyallup show and making a purchase, if there is not a FFL local to me at the show for the transfer, so I can drive locally to pick it up, I am not making any purchases at the show.
So Washington went from having amongst the best set of gun laws in the country to having some of the most strict, thanks in large part to financing from the Bloomberg group. The progressives of Seattle and King County keep trying more state legislation on modern sporting rifles, magazine capacity, ammunition sales, and a registry.
