Have you tried a system cache clear? Is your phone always looking for a 4G signal?
There are a number of threads on this forum with possible solutions, if you want to do a search.
Any news / update on this? I too have noticed that my Bionic battery isn't holding a charge as well as it did since the ICS upgrade last month. And that update has caused me other "grief" too - many settings were changed. Some more problematic than others - like it changed the setting on one of my email accounts to "delete from server" vs. "never" after deleting from device so suddenly emails were not appearing on my desktop. Not a good thing.