This is a thought that occured to me on my way to classes today; sharing it for feedback.
Omega appears before you, and after presenting an arbitrary proof that it is, in fact, a completely trustworthy superintelligence of the caliber needed to play these kinds of games, presents you with a choice between two boxes. These boxes do not contain money, they contain information. One box is white and contains a true fact that you do not currently know; the other is black and contains false information that you do not currently believe. Omega advises you that the the true fact is not misleading in any way (ie: not a fact that will cause you to make incorrect assumptions and lower the accuracy of your probability estimates), and is fully supported with enough evidence to both prove to you that it is true, and enable you to independently verify its truth for yourself within a month. The false information is demonstrably false, and is something that you would disbelieve if presented outright, but if you open the box to discover it, a machine inside the box will reprogram your mind such that you will believe it completely, thus leading you to believe other related falsehoods, as you rationalize away discrepancies.
Omega further advises that, within those constraints, the true fact is one that has been optimized to inflict upon you the maximum amount of long-term disutility for a fact in its class, should you now become aware of it, and the false information has been optimized to provide you with the maximum amount of long-term utility for a belief in its class, should you now begin to believe it over the truth. You are required to choose one of the boxes; if you refuse to do so, Omega will kill you outright and try again on another Everett branch. Which box do you choose, and why?
(This example is obviously hypothetical, but for a simple and practical case, consider the use of amnesia-inducing drugs to selectively eliminate traumatic memories; it would be more accurate to still have those memories, taking the time and effort to come to terms with the trauma... but present much greater utility to be without them, and thus without the trauma altogether. Obviously related to the valley of bad rationality, but since there clearly exist most optimal lies and least optimal truths, it'd be useful to know which categories of facts are generally hazardous, and whether or not there are categories of lies which are generally helpful.)
The problem does not concern itself with merely 'better off', since a metric like 'better off' instead of 'utility' implies 'better off' as defined by someone else. Since Omega knows everything you know and don't know (by the definition of the problem, since it's presenting (dis)optimal information based on it's knowledge of your knowledge), it is in a position to extrapolate your utility function. Accordingly, it maximizes/minimizes for your current utility function, not its own, and certainly not some arbitrary utility function deemed to be optimal for humans by whomever. If your utility function is such that you hold the well-being of another above yourself (maybe you're a cultist of some kind, true... but maybe you're just a radically altruistic utilitarian), then the results of optimizing your utility will not necessarily leave you any better off. If you bind your utility function the aggregate utility of all humanity, then maximizing that is something good for all humanity. If you bind it to one specific non-you person, then that person gets a maximized utility. Omega does not discriminate between the cases... but if it is trying to minimize your long-term utility, a handy way to do so is to get you to act against your current utility function.
Accordingly, yes; a current-utility-minimizing truth could possibly be 'better' by most definitions for a cultist then a current-utility-maximizing falsehood. Beware, though; reversed stupidity is not intelligence. Being convinced to ruin Great Leader's life or even murder him outright might be better for you than blindly serving him and making him dictator of everything, but that hardly means there's nothing better you could be doing. The fact that there exists a class of perverse utility functions which have negative consequences for those adopting them (and which can thus be positively reversed) does not imply that it's a good idea to try inverting your utility function in general.