AT&T announced this morning that their 3G network has received a speed boost. Top speeds should now reach up to 1.7 Mbps (to achieve this speed you must be using one of their HSUPA LaptopConnect cards) versus an old top limit of 1.4 Mbps. While I don’t have an AT&T 3G card to test their claims, I can share that on my Verizon V740 Expresscard, the data rates vary wildly. I’ve only been able to achieve top speeds (Verizon seems to top out at 1.5 Mbps) when stationary beneath a cell tower. The weaker the signal - the slower the data. Interestingly , the AT&T press release also claims a significant speed boost may be coming in 2010:

As HSPA technology evolves between 2009 and 2010 to HSPA+, peak speeds could reach 20 Mbps. AT&T plans to adopt LTE (Long Term Evolution) technology to reach even higher speeds in the longer term.

Link: AT&T reports 3G wireless download speeds of up to 1.7 Mbps for LaptopConnect Customers