I would definitely go to another body shop.
Metallic colors, especially whites, are extremely hard to match. Combine that with the required flex additive for a bumper and it's definitely not easy.
DO NOT go back to the same shop. If worse comes to worse right now, you can get the bumper resprayed somewhere else... and if that gets goofed up, they can get a new bumper for you. If the shop blends it and it still looks bad (which given their attention to detail is rather likely) then you have bad paint all over your hood and fenders. Combine that with the obviously cold temperatures and high relative humidity -> good paint work is hard.
Find out if your insurance has a guarantee for shops they recommend. State Farm, AAA, Geico, etc, all have guarantees that if the paint isn't good, they'll fix it. Call the high end dealerships in town and find out who they use, and hope there is a consensus.