My experience with service was during holiday times and all the centers were backed up. I live in Chicago so it was no brainer I send it to Chicago location but after 8 business days later still they have not looked at it, it pissed me off and I asked the lens back. Send it to Arizona location and I was waiting for an estimate with in 5 days actually estimate came the day after they received the lens and they shipped it back in a week.
They do charge shipping and somehow it was EXPENSIVE. Maybe with the insurance etc.? But if I am paying $320 for a repair and shipping it to them, its kinda weird to pay $30 ground shipping to Chicago.
Anyway, NY could be the busiest but if you send it to any other location and a part is needed, it comes from New York. Also pay attention to the working hours! Chicago location works half day and they service 2-3 other brands also.
If you are close to Arizona, send it there. Otherwise I heard good things about New York.