On Friday I upgraded my iPhone 3GS to the new iPhone 4S. One of the things that's changed in the 4S is that it's supposed to support HSPA+. Well not truly "4G", it should offer faster data transfers on AT&T's network. Before heading into the AT&T store to pick up my new phone, I decided to run a couple of tests on my 3GS in my car while parked in the parking lot.
My initial tests on the 3GS reported data xfer speeds around 970Kbits/s.
Once I had my new 4S in hand, I returned to my car to repeat my performance tests. I immediately saw the numbers jump to somewhere in the 1820Kbits/s—almost double the speed.
While this was not an exhaustive test by any means, it does appear that there is a nice speed jump on AT&T's network—provided your in an area covered by HSPA+.
Here's the screenshot showing my min/max results: