Looks like a consensus is forming.
I'll ask the shop to recheck the alignment with factory specs, especially the rear toe. I put about 700 miles a week on the car so any improvements related to the break in of the tires should creep up in a fairly short time. New tires didn't affect the handling feel of my weekender Boxster, but I've never had to have an alignment done on that car. It's possible in this case that it's a combination of the two.
Thank you guys so much for the input. I think you're on the right track.