Tim Minchin and His Orchestra, O2 Arena, London

Over the last week critics have showered Tim Minchin in stardust for his musical version of Roald Dahl's Matilda. While I look forward to seeing this fêted show, the prospect of revisiting Minchin's musical comedy hits didn't leave me quite as excited and I found myself leaving his arena show as ambivalent as ever about him.

Ambivalence is, at least, a feeling that the Australian performer, and champion of the secular and the rational, can identify with. Minchin eulogises it in one of his songs in which he wipes out the line between good and bad and asks us to remember that "arsenic, poo and crocodiles" are both "natural and organic".

That I feel neither good nor bad about Minchin stems from the fact that comedy is often the junior partner to his bold virtuosity, a virtuosity emboldened further tonight by backing from the progressive Heritage Orchestra.

Take "White Wine in the Sun", essentially the atheist's "Mistletoe and Wine", a poignant and sentimental composition and one of a number of ballads that won't stretch laughter lines much even if they do tug the heart strings, notwithstanding the amiable dexterity of a line like, "I'd rather break bread with Dawkins than Desmond Tutu/To be honest".

Despite its comedic title, the song "Rock'n' Roll Nerd" is similarly heartfelt, a semi-autobiographical, almost earnest, lament for a man too safe to ever be edgy: "He always dreamt of being a star/But he learned piano instead of guitar/Which in the Nineties didn't get you very far."

This is not to say that there are not some more direct anthems to vibrate the funny bone such as "Cheese", celebrating his dairy addiction with lines like, "I Camembert it any more!", and "Prejudice", a clever manipulation of the audience who think Minchin is singing about the N-word but is in fact singing about ginger-haired folk: "Only a ginger can call another ginger, ginger."

Whatever the variable and arguable comedic merit of his compositions the pure stand-up element to Minchin's act has always been considered the most suspect. Minchin recently described stand-up as "an artistic one-night stand", in the pejorative sense rather than the literal; however, the vague, uncertain and distracted persona of this wide-eyed, wild-haired performer can't mask that he's more practised at the banter now, if not fluent.

One of his talk breaks tonight sees him challenge the idea of sacred texts and ask if the Koran is really any more special than an edition of Harry Potter. It's reminiscent of an old Mark Thomas routine in which Thomas suggests that The Lion, the Witch and The Wardrobe could be quoted as a sacred text just as much as the Bible. The similarity is not important in itself but it's a reminder that today's political comedians aren't so obvious to spot as Thomas's generation were but are probably more numerous, and like Minchin, aim to set the rational against the reactionary.

It's true that Minchin can sometimes be blunt and less than satirical in his contribution to this struggle, as, for example, his new song about the power of prayer suggests, but you can't accuse this hybrid act of preying on easy targets.

Touring to 19 April (www.timminchin.com)