The new iPhone 4S made waves this past weekend with sales estimated to have reached 4,000,000 orders across the 3 carriers, AT&T, Sprint and Verizon. AT&T and Sprint both issued statements on Friday confirming brisk sales in retail stores across the country.

The new iPhone 4S, which was released two weeks ago at an Apple media event held at the company’s headquarters, has proven to be the Cupertino-based tech giant’s bestselling product. Available in several versions and two models, black and white, the new iPhone 4S incorporates a host of internal changes that include a new 8 mega-pixel camera that shoots 1080p HD video, a new A5 dual core processor that Apple noted increases graphics performance by 7 times and also increases battery life; as well as Siri, a new artificial intelligence application that functions as a virtual personal assistant. For most consumers, Siri will be the killer feature.

The Siri application is an iPhone 4S only feature. Siri acts as a personal assistant providing information and assistance for all kinds of tasks including reminders, getting information about weather and time zones, and even sending messages. The whole system is built around a database of commands and queries that allow Siri to learn user commands over time. This is the one feature that might possibly be a game changer.

In addition to Siri, Apple has also launched a new version of iOS as well as the new cloud storage, iCloud. There is also a new cheaper model iPhone 4 with 8GB storage available from Sprint, Verizon, and AT&T

Apple’s new iPhone 4S is available in 16GB, 32GB and 64GB, starting at $199, $299 and $399, respectively, with the purchase of a 2 year contract plan from AT&T, Verizon or Sprint.