Somebody suggested this in a different forum. I tried and noticed the difference. Thought it might help some folks. If your phone is slow and sluggish, try this:
Please go to settings>developers options>transition animation scale and make sure its on .5x and not 10x or it will be slower than a snail. Once you switch it make sure it stays there it took me a few times before it stayed put and started going fast again.
Also, try a system cache clean and/or FDR after installation if you have too many issues after the ICS update. It will resolve some or lots of problems.