I took it too, for quite a while. It did help my migraines, but now, actually, I went off of it, and using other meds, my whole migraine issue is just as good with not taking it.
The worst was when I went to the eye doctor and burst out crying when I couldn't remember my address. The eye doctor was so nice, he even knew that I was taking it before I said anything, just from the way I was acting. A day on topamax was like a brand new day, every day....the same Wendy's I drove by, I kept wondering when they built it....I learned so many new ways to go home (yep, you got it....the SAME way)....and let's not even contemplate going to the grocery store, even for one item, without a note. I also had huge hair loss and what hair I had left was in very bad shape.
So, for some people it works, but for anyone thinking about going on it....look into it and keep lists, your address (I am not kidding about this one actually) phone numbers, etc. in a place you know you can get to it just in case they slip your mind - - especially those first few days and anytime you increase your dosage.