Othello, Donmar Warehouse, London<br/>Ikrisma Kherol/ Impempe Yomlingo, Young Vic, London<br/>God in Ruins, Soho, London

Some theatre-goers are forking out more than 1,200 to see the tragic double act of Chiwetel Ejiofor and Ewan McGregor

Tickets for Othello, starring Ewan McGregor as Iago, are said to be changing hands, unofficially, for more than 1,200. I half expected to see Shylock making a cameo appearance during the scenes in Venice, to tot up the loans taken out by the audience. But the big question is, does the glitter of McGregor amount to theatrical gold?

His Iago is assured and scintillating at the off. In Michael Grandage's period-costume production, Venice is all puddles and dank brickwork, plus a soundscape of dripping. McGregor emerges from the shadows in black doublet and breeches. His red cropped hair has a spiky sheen, like an urban fox, and his ice-blue eyes glitter briefly with impish malignity. It's as if he is on some Saturday night spree of emotional vandalism as he shouts up at Brabantio's window, telling the old patriarch that his daughter, Desdemona, has eloped with the Moor. Occasional spasms of hatred for Othello, his military superior, shoot through his soliloquies too.

But this Iago peters out. No class aggro or psychological thread is seen through for which Grandage is to blame as much as McGregor. The effect is of a bunch of clips, some tantalising but without continuity, and this creates an impression of increasing shallowness rather than deepening mystery. McGregor, for example, physically massages his sap, Roderigo, not just giving his shoulders a rub, but frotting the guy's coccyx with his codpiece. Yet that homoerotic trait is then less incisively pursued in the great temptation scene, when Iago seduces Othello into losing faith in Desdemona and makes his climactic marriage-supplanting vow "I am your own for ever". Grandage also misses much of the dark comedy in this devilishly cruel tragedy. Iago's sidling insinuations should be far more horribly funny.

Chiwetel Ejiofor is remarkable in the way he paces and keeps a very tight rein on Othello's explosive jealousy. In Venice, he comes across more like a beautifully gentle guru than a soldier, speaking with an African lilt and wearing a simple tribal robe. He takes Brabantio's racist flak with saddened but near-saintly patience. In Cyprus, when he believes he has lost Desdemona's love, his slump into a quietly unhinged despair is certainly poignant and his violence, when it does erupt, is ferociously convincing. McGregor is actually outshone by Tom Hiddleston as well, a barely known newcomer and name to watch. His youthful Cassio (even though it, too, lacks continuity) is startlingly charismatic and dangerous in its own way, naively mixing professional duty with womanising.

As for Kelly Reilly's Desdemona, I'm afraid I wanted to throttle her in Act One when she behaves like some infuriating coquette, with a high-pitched babyish voice. She stands in the war-council chamber, snuggling up to Othello with what looks weirdly like a faux display of gazing adoration, head simperingly on one side. Now and then she casts a victorious glance, with snaky narrowed eyes, at her sidelined father. She looks more evil than Iago. I wouldn't touch her with a gondolier's bargepole.

I suspect some male viewers may have a very different reaction but given the smug glances I presume Grandage doesn't think her minxish tricks are charm itself. Maybe this is, in fact, a staggeringly bold, anti-idealised interpretation, pushing the idea that she's a daddy's girl turned silly flirt. Maybe, when Brabantio bitterly predicts she will prove serially treacherous, we are meant to think she might. For me, Reilly becomes miles more sympathetic when shockingly struck across the face by Othello she suddenly looks like a vulnerable shaken little girl and, though she rallies, never quite trusts him again.

Finally, to cut back to that soundscape of dripping, this production gets more and more drenched by Adam Cork's obtrusive movie-style soundtrack as it cornily attempts to pump up the tension. Every time Iago starts machinating, we hear a sinister subterranean rumble, as if Satan is running a Tube line under the Med. As for the whirring throughout the temptation scene, was it meant to be cicadas or was it the Fiend, in an idle moment, just rewinding his video cassettes? To be fair, the Donmar's official box-office prices with day seats still available are very reasonably priced. But for 1,200, I'd certainly have felt shortchanged.

Far more inspiring is the South African musical reworking of Dickens's A Christmas Carol aka Ikrismas Kherol, directed by Mark Dornford-May of U-Carmen renown. It is performed by a troupe of black actors, including Mbali Kgosidintsi , pictured right. Many are from poor townships. Pauline Malefane's Scrooge is a mine owner and mean iron lady, refusing to sponsor the ailing Tiny Thembisa's schooling. As if epileptic or possessed, Thembisa falls down and Marley's ghost speaks, rather thrillingly, through her. Then upbraided by the spirit of Christmas Past, Scrooge journeys back into her own childhood, with projected footage like a home-made documentary of a real, terribly impoverished shanty town. She finds her humanity and, symbolically, her singing voice again through remembering the carolling in the chapel and her self-sacrificing sister, who prostituted herself and caught Aids. This probably sounds preachy. In a way it is, but this update brilliantly reinvests Dickens's message about sorely needed charity with powerful immediacy. The African singing mixing hymns with tribal drumming and welly-boot dancing is joyous. And the fact that all this is done on a shoestring creating the mine's din with chains dragged across oil drums makes it all the more wonderful.

I was slightly less wowed by Impempe Yomlingo, which is Mozart's The Magic Flute re-orchestrated and based around a Xhosa initiation ritual. Though Malefane is a splendidly witchy Queen of the Night, with her hair like glittering tree roots, the company's rough edges are more exposed here and Dornford-May's stagecraft looks rudimentary. That said, when the classical arias and ethnic ululations fuse, it's euphoric. Mozart would surely have loved the cheeky wit of turning his orchestra into eight marimbas and the magic flute into a silvery jazz trumpet.

God in Ruins, by the writer-director Anthony Neilson, proves to be another radical rejig of A Christmas Carol. Brian (Brian Doherty) is a stupendously dishevelled, substance-abusing producer of reality TV who spends Christmas tripping but also trying to re-establish contact with his estranged daughter. God in Ruins was clearly a challenging RSC commission, devised with an all-male 11-strong cast. The outcome is scrappy, but the comic anarchy is also a blast, not least when everybody boogies around wildly, in angel and reindeer costumes, in a snowscape of cocaine.

Neilson also engineers great sharp twists, whipping the rug from under your feet. He's not forgotten how to chill either, with Brian at the unsettling heart of the play pretending he's a young woman in a pornographic chatroom. Sitting slumped in the blue light of his computer screen, he starts speaking with the disembodied voice of a girl. Very spooky.

'Othello' (0870 060 6624) to 23 February; 'Ikrismas Kherol' and 'Impempe Yomlingo' (020 7922 2922) to 19 January; 'God in Ruins' (0870 429 6883) to 5 January

Further viewing Mark Dornford-May's award-winning 'U-Carmen eKhayetlitsha' (DVD, Tartan)