According to New York Apple retailer Tekserve, the Retina MacBook Pro took just 13 minutes, edging out the 2012 models of the MacBook Air, which posted a 17 minute upgrade time. The difference could be chalked up to the two extra cores in the 15-inch laptops quad-core Ivy Bridge processors compared to the MacBook Airs dual-core CPUs.
In contrast, Macs that are still equipped with mechanical hard drives took three to four times longer to complete their Mountain Lion upgrades. The worst of the bunch was the 15-inch MacBook Pro that uses the traditional unibody design, posting a 57 minute time. Its 13-inch brother barely made an improvement, taking 55 minutes to complete the update.