In regard to the illusions (or is it reality?) of A Midsummer Night's Dream, one of the wonderful things about this play is that the "dreams", or magical occurrences (which could be illusions, too) can be interpreted many ways. Let's look at the example of Titania, the Queen of the Fairies, succumbing to the love-juice and falling in love with Bottom the Weaver (who is wearing the ass's head put on him by Puck.)
The love-juice has made the beautiful and supernatural Titania fall in love with a figure of the utmost ridiculousness. She awakes and immediately believes that Bottom is the most wonderful creature she has ever seen. "[Awakening] What angel wakes me from my flowery bed?(120, Act III Scene i) While this is certainly an illusion -- Bottom is a "rude mechanical", and, furthermore, his head has been turned into a one of a donkey, Titania, perhaps feeling wounded from her quarrels over the changeling with her husband Oberon, would probably enjoy the distraction of an "angel". So, while it is clear that Titania is not in her right mind, and is under the influence of the drug (which puts Puck and Oberon in a particularly reprehensible light, by the way) the illusion of Bottom in the ass's head becoming an angelic lover for the Fairy Queen might be considered some kind of wish-fulfillment on Titania's part. After all her marital strife Titania would probably welcome a lover, and a gentle, biddable soul like Bottom (who would never threaten or dominate her as Oberon does) might be a nice change for her. The fact that Bottom has the head of an ass (a pun in itself) might be interpreted as Titania's self-loathing, too, but that seems unlikely.
The antics of the four young human lovers (Hermia, Helena, Demetrius, and Lysander) can definitely be seen as a kind of subconscious desire for more than one partner. The switching of alliances is bewildering, and perhaps in keeping with the fickleness of affection in these young people, the quick switches are just as quickly resolved. So the desire to trade partners might be viewed as not a deep-seated desire, but rather a passing fancy. On Hermia's part, on the other hand, her desire to go with Demetrius (or to have both young men pursue her), though she has professed her love for Lysander, could be an expression of her desire for self-preservation. Hermia, an Athenian daughter, falls under the law that she could be put away in a convent or even killed if she marries without her father's consent. She has eloped with Lysander -- if she shows up in Athens with Demetrius, might her reputation (and her life?) be saved?
But again all these people are victims of Puck and Oberon and their powerful love-potion. Puck and Oberon, the fairy-boy messenger who goes every where, and the King of all the Fairies, can be seen as subconscious manifestations of the audience's desire to control to the characters in the play (and, by extension, people in the real world). This display of power -- of being able to control that least controllable of desires, that of affection or love -- is a common desire of mankind, whether for themselves or for others. There have been "love potions" of various kinds for centuries, if not for millennia, so the fact that the whole plot turns on Puck's dispensing of this drug can be seen as a wish-fulfilment for humanity's desire for supernatural control of themselves and others, especially in the sexual arena.