I've been on the Potiga for about a month and a half now. I'm up to 200mg 3X per day, and still taking Keppra, 1000mg/day. My doctor wants me to get up to 900mg of the Potiga, but I've been going slowly.
I don't know how it reacts with Lamictal. As to your other concerns, I haven't noticed any blue skin issues, or anything with my eyesight so far (knocking on wood!). I also haven't had the urinary retention issues, which seems to be the big concern.
I like the medication so far, and have had minimal physical side effects. The big one is I tend to get very dizzy about 10 minutes after taking the pill, but it goes away within 20 minutes or so. The cognitive issues are more frustrating. I have trouble getting words out, especially in the hour or so after I take the pill. I tend to stutter and slur. Also, if I try to drink any alcohol, I feel drunk after a few sips. My doctor never mentioned alcohol, but it says not to drink in the literature.
It also says acetaminophen is a "major reaction", and he never mentioned anything. I had a cold a few weeks ago and took a bunch of cold medicine with Tylenol. Won't make that mistake again!
Overall I am still wary of this drug, as my doctor seems to know very little about it. He said I am only the second patient he has prescribed it to. Yet, this is the eighth drug I have tried this year, and it seems to be the best so far.