There are lots of posts in this forum about people having problems once they have updated the Sensation to ICS. So it will not always follow that an upgrade will work better. Sometimes it can cause problems.
I was (and still am) in the same position as the OP and I posted a thread a while ago to try to find out just how widespread these problems were, as it is true to say that bad news travels further and quicker than good news. However I got very little response one way or the other.
My advice to the OP is to go back through those old threads and have a good read. Then make your own mind up whether to risk it or not. Me? I am still not sure, because at the moment my phone does all I want it to do.
HTC Sensation (Giffgaff UK)