Geodon was awful for me, and Topamax has been awesome for my migraines...I have only had a few over the past few years whereas I used to get one almost every day. My neuro said its about a 50/50 split for people having a good or bad reaction to Topamax. I have had no side effects at all (except some weight loss). I know it can sometimes effect you cognitive ability (as mentioned in the other threads), which can be one negative side effect, but this did not happen to me.
It's worth trying out though and seeing it through your max prescribed dose to see how you do, if you can. It's been a life saver for me since I had migraines since I was about 7. And I did lose weight, too, as mentioned...it effects how your metabolism works. Hugs to you and I hope you have a good outcome with it.