However, while not entirely predictive, studies shown that idealization of marriage and/or the person you marry has a positive correlation to length and happiness in marriage. It's not terribly surprising - going into something with optimism seems to generate a more positive outcome. Other longitudinal studies support this indirectly, with concepts before marriage playing a fairly significant role. The argument here would be that false expectations are a downside, however it doesn't seem to be a case (least as far as it relates to personality or effect). Hard to say for sure, since it's not really looked at directly... but in all of these situations, the major effect is the lack of communication. Ideals that are not communicated are an issue, as are money issues, sex issues, children issues... etc. But if you look for issues in idealization, you can find them... that doesn't mean it is endemic to a particular type, or that it is, on average, a negative thing (in and of itself). It is very likely that a forer effect can modify a marginally positive trait into a negative one simply because when identifying negative impacts, one makes the connection given the hypothesis (in this case, INFx are most unhappy), when there may be other causes.
Another interesting thing about this is that the top complaints in relationships really have very little to do with personal interaction. Most people can pair up and be happy, given that the basic framework is in place. It's issues like money, children and mate-guarding that top the list... when you regress issues, there is some connection to personality... but more interesting is if you also look at the correlations to certain types and the big three issues, you find the same correlation.
So, in my view, one has to be very careful assuming a given issue in any personality, then one must be careful assuming the explanation of the parts of the personality are responsible, and finally, one must be careful not to see the personality at fault and not the indirect effects of the personality.
(FWIW, as I remember it, ENFJs were the most positively associated (equivalent to other personality theories) to positive relationships... but keep in mind the fuzzyness I talked about above. )