I have been using my girlfriends iPhone 4 to compare data speed results with my 4s. Both are on AT&T. I live in Oxford Mississippi. According to the AT&T data map, I should have HSDPA data speed here. I have tested both my 4s and my girlfriends 4 using speedtest.net app and both have similar results within 1mb of each other. Sometimes the 4 is faster and sometimes the 4s is faster but the 4s does not outperform the 4 by any margin. I then went to Memphis this weekend and while I was there I remembered to test the data speeds of both phones at different areas of Memphis. This is another city which is supposedly a HSDPA+ area. During the tests I again got similar results from both the 4 and 4s with 1mb of each other. Around 4mb download and 1mb upload consistently. I have so far not found an area where my 4s was able to get over 6mb of data speed and outshine the 4 in speeds. Take this with a grain of salt because there are obviously plenty of other big cities that might have better HSDPA+ speeds.