Varies. Within a 3g network, my card has (have proof via different online speed tests) hit 1.5+ Mbps (1.5 megabyte per second)

Out side a 3g area the card will generally run on the edge network, full service in this area I'll get 2-3 times faster then dial up. 100-140 kbps.

Just did a another test via testmy.net, here's my results.

You can use the validation link to "VERIFY" my results
:::.. Download Stats ..:::
Download Connection is:: 1275 Kbps about 1.3 Mbps (tested with 1496 kB)
Download Speed is:: 156 kB/s
Tested From:: http://testmy.net/ (Server 2)
Test Time:: 2007/05/02 - 8:55am
Bottom Line:: 22X faster than 56K 1MB Download in 6.56 sec
Tested from a 1496 kB file and took 9.609 seconds to complete
Download Diagnosis:: Awesome! 20% + : 142.4 % faster than the average for host (mycingular.net)
D-Validation Link:: http://testmy.net/stats/id-H3FQ9WCJ4
User Agent:: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.3) Gecko/20070309 Firefox/2.0.0.3 [!]

 

Nope that would be MegaBit not MegaByte (8 bits to a Byte)

I could see 1.5 Mbps tops on HSDPA network.

However .. it is more than just finding a 3G (GSM) cell .. that cell has to support HSDPA. I would assume that Cingular is expanding its presence everday in lager cities but not every cell in even the largest cities are both GSM/HSDPA capable. Even then .. there are deadspots even in large cities.

The good news is that if you are headed to Europe .. GSM /HSDPA is the standard... the bad news is the coverage here in the US

Why Verizon and Sprint are better is that CDMA supports data packet transfer as well as digital voice at higher speeds. So you get faster service even in many remote areas and the Braodband technology is even faster (3Mps vs 1 - 1.5)