After making available a custom ROM based on leaked Sensation XE Ice Cream Sandwich RUU, RCTeam has released the original Rom Update Utility for both Sensation XE and Sensation smartphones at XDA.
Sensation XE RUU has been available for the last few days but the classic Sensation RUU was released only a few hours ago. It is important to understand that these RUUs are pre-release software, so it is pretty normal to found bugs and other issues that is why normal users should stay away. These are meant only for advanced users; do not flash them unless you know what you are doing.
However, if you want to give ICS a try, you can grab the related downloads from here. Flashing RUU is a pretty easy processor, all you have to do is connect your phone via USB and run the RUU exe.
You will have flash CWM recovery later, so that if you want to get back to GB, you have a custom recovery to flash other ROMs. All the related instructions and details are given at the previously mentioned link.