Here's a sampling of what they had to say:
Mark Shenton in his Theatre.com Review: "There's a lot that's borrowed—and quite a bit that's blue—in Avenue Q, which is nevertheless that rare thing: a genuinely original new musical, not based on a pre-existing film or book. But it is also full of cultural touchstones that make it both familiar and accessible, yet entirely its own animal… Jon Robyns, Julie Atherton, Simon Lipkin and Clare Foster are the superb, selfless quartet who switch with sublime versatility between puppet characters, while Ann Harada the sole member of the original U.S. company to recreate her performance here is joined by Sion Lloyd and Giles Terera as the human components. All in all it is impossible not to fall in love with director Jason Moore's ingenious and good-humoured production."
Benedict Nightingale of The London Times:"Just like your life, only funnier," boast the ads outside what used to be the Albery Theatre and has now been renamed the Noël Coward. Well, um, yes, that might be so if a I lived on the dangling tip of Lower Manhattan and spoke through a large glove-puppet and b I didn't laugh twice as much on an average day at home as I did last night at the musical that won Robert Lopez, Jeff Marx and Jeff Whitty the Tony Award in 2004. But there are puppets and there are songs, and they do much to cover up the sentimentality and predictability… I wonder what the great Noël would have thought of his theatre's christening party. He'd have enjoyed the youth and energy. He'd have regretted the relative lack of sophistication. He'd have deplored the jokey teddy bears and the cloying tribute to altruism that closes proceedings. Just like me last night."
Dominic Cavendish of The Daily Telegraph: "Gosh, gee, golly and all things beginning with the letter 'g,' what a disappointment!… Maybe the zany idea, combined with the show's gilded reputation, will be sufficient to keep the crowds coming. But either something has been lost in translation or this dinkily alternative but incredibly lightweight affair, staged now with a mainly British cast, was never as much cop as its New York admirers have been claiming. We were told to expect Sesame Street meets South Park, sort of, but almost nothing I heard or saw last night actually lived up to the violent collision of styles and sensibilities that such a description implies. Robert Lopez and Jeff Marx's tame beast of a show lumbers up a cul-de-sac of one-note satire before hitting a brick wall of anodyne schmaltz. By the second half I found myself mentally rechristening it Avenue ZZZ."
Paul Taylor of The Independent: "What's appealing about the piece and Jason Moore's bouncy, enjoyable production is the total absence of jaded cynicism. What's less attractive is the lack of real bite. Compared to Jerry Springer: The Opera, another satiric spin-off from television, Avenue Q is about as genuinely subversive as Friends. All the same, I found it, intermittently, a lot of fun. Most of the human cast has to pull off the extraordinary feat of acting and singing and passing as American, while manipulating their puppet alter-ego, and several have to do so in a variety of roles. Technically, they are a complete success… The spirit of Avenue Q is humane and healthy. After all, it's not every show that manages to be tongue-in-cheek and hand-on-heart, while having its arm up a puppet's bum."
Nick Curtis of The Evening Standard: "This affectionate adult spoof of Sesame Street is a one-joke show. Fortunately, it's a pretty good joke, for a while at least. Unlike the upbeat, educational characters of the TV series, Avenue Q's puppets tell racist jokes, screw around, download porn and generally get depressed by their crappy lives. The first few times we hear a goggle-eyed sock in a wig swear, it's undeniably funny. But even if we accept it as a wider satire on American culture or an even bigger mockery of universal human weakness, the puppets-as-real-people gag eventually wears thin. And although Avenue Q is very well executed and sporadically hilarious, I suspect it's both too tame and too culturally specific to enjoy the same success in London it has had on Broadway… Avenue Q feels like it could have become a cult hit at a small venue but I suspect it may founder in the West End. Shame. I really wanted to like it much more. It may only have one joke, but it is a very good joke."