Most users that have flashed this radio are reporting increased download speeds as well as HUSPA upload speeds and better latency/ping times. HOWEVER, several users have reported an increase in the amount of heat dissipated which, combined with run-away apps that are constantly churning data, could cause your phone to get hot.
There have been a lot of questions about inconsistent speed tests. I've even seen some posts claim that they're download speed has gone down. Please use some common sense here and understand that there are many factors that come in to play including SpeedTest, local towers, network congestion, etc.
Also, please be advised that you must use RSD Lite under Windows to flash this radio.
All credit goes to NFHimself from whom I got the idea and who helped me work through the kinks.
Attached is a zip file containing 2 separate sbf files. You will want the SBF for the 1.87 baseband radio which is the same one that shipped with the Telstra 1.4.2 update. It should not require a reset as it's the radio only, and I have successfully flashed it to my ATT phone using RSD Lite giving me upload speeds slightly higher than my dl speeds (currently showing just under 2Mb).
I am also providing a radio only sdf of the stock ATT radio that recently shipped so that you can go back if need be.
Keep in mind that while it did work for me, this has not been thoroughly tested and I will not be responsible if decide to use this and you brick your phone.