The concept of IQ is a little outmoded. The amount of knowledge one possesses may be objectively measured; the same cannot be said of the facility to use knowledge. We do have many scales that provide a practical evaluation, but these too become progressively uncertain as we move towards higher intelligence groups. One reason may be the paucity of study cases. By definition, high intelligence is an infrequent occurrence. In any case, the fact that IQ is not exactly a scientific concept is sometimes enthusiatically extended to conclusion that high IQ does not exist. The fallacy of such an argument is apparent. Not everything that can be observed, even utilized, is easily measurable. A lack of formalism certainly does not mean that the phenomenon is absent.
People with high IQ are liable to be maladjusted just like people possessing any other extreme trait. The severely maladjusted cases usually consist of people with very high capacities in a particular area with inhibited interest or capacities in others. Some recent research suggests that this may even be a form of autism. The major problem for the rest of the cases is usually a lack of sounding boards (read, a feeling of alienation). High IQ societies and clubs sometimes go some distance in ameliorating this. More likely, the solution for this dilemma, like most others, comes with time. High intelligence is like any other gift; only it more often than not opens a can of worms for its owner. On the other hand, the nature of this gift allows for a repackaging of the worms, besides other achievements. So, after all, does this 'gift' warrant the pride it so often inspires? I would answer, does any gift?
I suspect that, in terms of sheer computational strength on a cardinal scale, the difference between IQs of, say, 155 and 100 would not be great. But for all practical purposes that is beside the point, for the tasks that may require high computation, like vision, come easily to everyone. It is the remainder that we observe as differences amongst individuals. A good article on Hi-Q can be found at http://www.prometheussociety.org/articles/Outsiders.html.
I'm a member of the Triple Nine Society, a high IQ organization for people with IQ over 99.9th percentile of the population. You can visit the TNS website at http://www.triplenine.org/