Try re-setting your network settings. I bought an ip5 yesterday, was only getting about 6mbps download when I was getting about that with my 4. Strangely, a mile away from my house i was getting 50s.
Called ATT, they said that they have four towers in my area, one of which (the one closest) was being worked on off and on for the next three months. Recommended that I re-set the network settings.
Settings/general/reset/reset network settings
I did that and jumped to 38-39mpbs download, 19-20 upload!
worth a shot