Side effects are different for everyone, but I think that if you're going to get them with Topamax, you're going to get them right away.
I was on Topamax all of 2007, off 10 months, and just recently went back on it (long story, not applicable). I have Bipolar 2, BPD, and PTSD.
Main side effects for me are carbonated drinks taste AWFUL! I try to have fun with it though by having my friends buy me various sodas and have me rate them on the "ass-o-meter" (1 to 10 scale, 10 being the worst) of how terrible they are. Might as well have some fun with it.
The "word-find" problem is also a biggie for me too, and again, I just put it out in the open that a medication I'm on does this to me. We all have a good laugh about it when I can't remember that the big round thing covered with cheese and pepperoni we're having delivered for lunch is called "pizza".... It's only irritating when you really want to think of a witty word in an argument but can't. Oh well.
I also get the tingly hands and feet, and also lips from time to time. No big deal though, considering the alternative. I've been on various assortments of medications over the years, and Topamax has worked the best for me in spite of the side effects. However, I suffer from Fibromyalgia, so I'm willing to put up with a heck of a lot of irritating side effects in order to not suffer the pain. Everything is a trade-off.
Something a lot of folks won't tell is that people on Topamax should seriously avoid sun exposure or suffer rash. The other big side effect is a long string of upper respiratory infections. I got Strep, Mono, four sinus infections, a burst ear drum, fluid in my lungs, and was basically constantly sick. I later found out I am allergic to pretty much everything, so I don't know how much of what caused what, but all that info was after the fact.
Just keep informed, and keep each other informed. Don't trust the word of one doc or the drug reps. Trust the words and the histories of the people taking the meds!!!
Good luck everybody!