I have been on it for 3yrs. I have been maintained on 2oomgs per day.
I did experience the one thing you mentioned, I thought I was losing my memory and ability to write, my doc said this is common, it lessens, and dosage has a big influence (sp?)
A big culprit with this memory thing I have found during the times I use Ativan for occasional nite anxiety, but not with Klonopin (it's cousin) if I am having an oncoming attack.
Lamictal for me has worked the best for my mild bipolar (BP-II) compared to past meds I had tried.
Stress this problem with your pdoc, he or she will work with you, perhaps even change your dosage gradually.
Hang in there, in my heart I feel things wil get better for you, like anything it takes time.
I sincerely wish you lots of luck with this.

Please take care,

DE