According to AT&T's new iPhone website, the maximum download speed you can expect to achieve with the device is 1.4mbps.  That is much different than typical 3G phones like the Motorola Q for instance which comes in at a hefty 3.6mbps.  HSDPA data cards can get as high as 7.2 mbps.  What gives?! 

It is unlikely to be a webpage error because the 1.4mbps speed is also quoted in the official press release.  While this may still be twice as fast as the previous iPhone, if true, it won't impress anyone who has used full 3G enabled devices.

Motorola Q?  3.6 Mbps!!!

Update: For more information, check out Gizmodo's writeup.  According to them AT&T caps all 3G smartphones.  If that is true, why do they list the Q at 3.6mbps?  From Gizmodo:

But the iPhone 3G is rated for 1.4Mbps, a nice clip but not the 3.6Mbps downstream that AT&T's HSDPA is capable of. (The carrier loves to brag that it'll have 7.2Mbps by the end of the year.) So why not crank up the iPhone to those better data rates? Turns out, according to AT&T people we talked to, 1.4Mbps is the capped bandwidth for all mobile smartphones on the network for a few reasons.

(UPDATE: AT&T is saying they're not capping the phone at 1.4mbps, but that's what its capable of doing now, due to factors below. There's no difference except intent, and AT&T is careful around words like "Cap" these days.)

A major one is battery life—the faster you burn, the faster your battery dies, so going full steam at 3.6Mbps would cut you well short of that nice round five hours. A second one is cell site congestion and backhaul (carrier-speak for size of the wired dataline that connects cell sites to the actual telecom infrastructure). While everyone at AT&T, from the top down, is adamant that AT&T is "comfortable" with their ability to meet the huge data draw once 3G iPhones hit the streets, it's not like the pipe is unlimited.

AT&T wasn't able to give a breakdown as to how many of their towers have fiberoptic pipes as opposed to slower copper T-1 lines. Nor could they say how quickly they could add capacity to a site that is pummeling their demand expectations, since it varies from site to site. Ones in dense urban areas are loaded up with more backhaul and can handle more users than one closer to the edge of their 3G footprint. Still, generally speaking, more users on a site means more congestion, so if you're slurping from a site that's really slammed, it will be slower. As with all radio technologies, proximity also matters. (Hint: For the absolute fastest speeds, wait until 3am and then go sit right next to your favorite cell site.)