I take 200mg for partial seizures, added it to neurontin about 9 months ago.
At 300mg I lost the ability to type correctly and would forget what I was saying in the middle of a sentence. I forgot phone numbers and lost a ton of weight. My doctor said that meant I was on too much. I'm glad he put be back to 200 instead of upping the dose, which is what I see most people doing - adding more. I am taking as little as possible to keep the seizures away, and I feel pretty good on it.
My side effects currently are constant movement of my jaw and tongue, and my new side effect is a strange involuntary movement of my arms and legs. I especially notice it when I'm on the computer and I move the mouse, my arm jerks. (At least it jerks in the direction I want it to!!)
Overall, I am happy with it and feel lucky that I'm not having any terrible side effects. The jerking thing is a bit concerning since it is new and I hope it doesn't get worse.
I do think my skin has gotten messed up - not quite acne, but redness under the skin. No bumps though.
Oh - the tip of my tongue gets numb about 15 minutes after I take it. Weird.