An internal AT&T memo that was leaked today is full of very impressive number regarding the iPhone 3GS — numbers that once again show why AT&T's exclusive contract with Apple to sell the iPhone in the U.S. is so important. The iPhone 3GS's launch gave AT&T its best sales day at its retail stores — ever, its second largest traffic day at retails stores, the most transactions it has ever processed in a day, the most orders through att.com in a single day ever and the biggest features sales day at att.com ever. Oh, and it led to the most upgrade eligibility checks ever, which is not surprising at all, though most were probably disappointed . What's crazy about all this though is that while many people were expecting the iPhone 3GS launch to pale in comparison to the iPhone 3G launch, it actually exceeded it in just about every way when it came to actual sales (at least through AT&T's stores and online). The lines may have not been as long at stores because of pre-sales, but sales overall exceeded the 2008 launch day numbers, and all of the heavy holiday shopping times. And apparently iPhone 3GS sales exceeded the iPhone 3G launch day sales by noon Central time.