I posted this in another similar thread, but since it helped me, and may help others, i am posting here too...
I had a slow bionic after update. I disabled the window and transition animation in developer options, and yes, that made a big improvement. So i tried wiping the dalvik, that made no difference. I talked with a verizon rep, and they mentioned among other things to start in safe mode. That made the most sense, because if i saw an improvement, i might link it to an application, without having to do a factory reset. In safe mode the phone did work much better and much faster. The thing that was really obvious to me was hitting the search button. That was noticeably slow before safe mode and noticeably faster after safe mode. In safe mode i noticed two desktop icons failed to load, one was calendar pad, and the other was circle battery widget. Sadly, I could not uninstall them in safe mode, so i rebooted normally and first uninstalled circle battery widget. That solved the problem, that was the app that was the culprit. So, if you have a slow bionic after the ICS update, the main reason may be a problem app. I would rather uninstall apps that i can always reinstall, then do a factory reset and possibly lose data and take alot of time. I don't know about paid apps, so do your research before uninstalling paid apps, or apps that store your data, such as bookmarks passwords etc. Make sure you are comfortable to delete apps before following this advice. Here is how i got into safe mode....
1) turn off the bionic and wait till it powers down
2) press power button until you see the motorola logo
3) as soon as you see the motorola logo press (at the same time) the volume up button and the volume down button.
4) do not stop pressing the volume up & down until you feel the phone vibrate
5) the safe mode text will show in the lower left corner of the screen letting you know you are in safe mode
6) find something in your life to be passionate about and keep dreaming