Despite an initial lackluster response, excitement has been building for the release of Apple’s newest iPhone, the 4S.

On Friday, it officially goes on sale to the public.

Despite disappointment that the form of the iPhone 4S is identical to the previous iteration, each of the wireless carriers, AT&T, Sprint and Verizon, have sold out of online orders for the phone, indicating higher than expected demand. Apple said that those orders topped 1 million during the first 24 hours the phone was available — beating the previous single-day online order record held by the iPhone 4.

Stay tuned as we update with reports from Apple stores, Twitter and around the Web on the first day of sales, and feel free to share your reactions and experiences in the comments below.

At 7:45 a.m., 15 minutes before the doors of the downtown San Francisco Apple store opened, the line of buyers snaked around the corner and halfway up the block. That is considerably shorter than in years past when the line circled the block and then some.

On reason might be that strategic shoppers stood in line outside nearby Verizon, Sprint and AT&T stores. At the AT&T and Verizon stores on Market Street, within a block or two of the Apple store, about 35 were standing outside each store. An AT&T store further down the street also had about that many people queued.