since the phone was first released, and an improvement in the performance of Bluetooth on the phone. The entire update weighs in at 150MB which the HTC One S will swallow faster over Wi-Fi. So we would suggest that you use Wi-Fi while updating the phone. That is, unless you need the update to improve the Wi-Fi connection on your HTC One S. Other items on the changelog include improvements in showing links on email, helps prevent the device from crashing, prevents streaming music from streaming, and brings improvements to the UI. For the complete list, click on the sourcelink.
T-Mobile says to receive the update, your HTC One S must have Android 4.0.3 and have software version Software version 1.53.531.76 710RD or 1.84.531.2 710RD. The battery on your phone should be at least 50% charged with at least 140MB of storage free. The phone cannot be rooted for the update to be received.
source: AndroidCentral (2), (1)