I do fine with topamax - 100 mgs at bedtime. Seems I hear people who take it for other than migraines and not at bedtime are the ones who tend to have the most problems with it.
It tends not to work and gives them the most/worst side effects.
While I have some of the same symptoms you report - insomnia, cogfog, depression at times - I had all those things before topamax, and they're no worse now. But no way I could live with the way those migraines were.
I do get how any med can be great for one, disasterous for others - ADs are horrible for me, used several for pain, always bad results.
When the side effects do not outweigh the benefit, there are usually other meds to try.
Forums like this are a priceless source of advice from other people in that way!