Higher than average IQs among those who have the disorder, however IQ can vary between alter states. During the Cold War, hundreds of gifted children were inducted into experimentation programs focused on manipulating dissociative states, so anecdotal reports from a variety of caregivers show higher than average IQ among these patients.
Gifted people are more likely to suffer from Multiple Personality Disorder than the general populace. The gifted mind works in a very different way than those who are not gifted and that need further research. Multiple Personality Disorder is a complicated problem that may not be clearly understood at this time.
I do not believe the gifted are afflicted more with multiple personality disorder, I believe it appears equally among the populace. Many have tied ADHD, Autism, and other disorders on the Autism spectrum to those with higher IQs. I think this association is common and more than likely correct. I have not heard or read anything that indicates that multiple personality disorder is somehow connected to the gifted.
The gifted are no more likely than the general population to be afflicted with multiple personality disorder. The gifted may be more likely to be diagnosed, however, given the extreme focus paid to their cognitive abilities because of their "giftedness." So, while not more frequent, it may be more frequently diagnosed in the gifted.
No, I do not think that the gifted are afflicted more with multiple personality disorder, because those who are gifted usually just have more reason to know of the mental health defect. With a gifted person, their defects are so much more obvious because they are so high functioning in the first place.