The Apple Store app for the iPhone has enabled Apple to revolutionize retail and mobile shopping shopping thanks to features such EasyPay, Personal Pickup, and assistance from the store's Specialists. In today's 2.2 update, Apple has added Express Checkout and new location features which focuses on online shoppers and customers picking their orders up from their nearest Apple Retail Store.
Express Checkout speeds up the process of making purchases through Apple's online store by using your existing payment and shipping options. You can simply complete your order by tapping on the buy button for the items you want to purchase, selecting your options (if applicable), and checking out, then entering the password associated with your Apple ID. You'll have to sign into Express Checkout through your Account Settings in the Apple Store app (on each device), and agree to the terms of service to use the quick pay feature. A FAQ for Express Checkout is available for your perusal online.
If you have an iPhone 4S and are picking up a purchased item from your local Apple Retail Store, your device can let the specialists know you're arriving so that your items are ready for pickup before you reach the storefront. By enabling Location-Based Alerts and setting your pick up information in the Account Settings, items for pick up will be waiting for you to carry out when you reach your Apple Retail Store.
The Apple Store 2.2 update is available on the App Store as a free update and download.
Edit 4:03 pm: Edited title to clarify that faster, location-based pickups are not a part of Express Checkout, but a separate feature available on the iPhone 4S.