Nearly four years after London mayor Boris Johnson called on designers to reinvent the iconic Routemaster bus, the winning design by Thomas Heatherwick has finally gone into service. Costing a reported £1.4m each, the new buses don't come cheap, and for now only eight of them have gone into circulation, running on route 38 between Hackney in east London and Victoria station. So what have design critics made of the new bus for London - is it an expensive vanity project or are we witnessing the birth of a design classic?

Well, it's probably too early to tell, but most critics seem to lean towards the latter. The Guardian's Justin McGuirk, has welcomed what he calls 'the Routemaster's triumphant return to London'.

'It is not until you've taken a ride on the new Routemaster that you become fully aware of how unlovely our current fleet of buses is,' writes McGuirk; concluding that, 'If [Labour's mayoral candidate] Ken Livingstone wins [the election for London mayor, which takes place on 3 May], he shouldn't write this off as one of Boris's whims but embrace it as an investment in the daily life of Londoners.'

The Telegraph's Andrew Gilligan is broadly positive, too, though he does express some reservations about the design - presumably that it is not enough like the old Routemaster, which many people seem to have forgotten was poky and cramped inside. 'I have reservations about the design, writes Gilligan. 'Some of those reservations remain. But the more I see it, the more I like it.'

Gilligan continues: 'The old Routemaster's half-cab is no more (boo!) But its slatted, wood-effect floors, its classic dark-red interior, its conductors - and, above all, its platform at the back - return,'

The Independent is also full of praise: 'Aesthetically and environmentally, the bus impresses The designers have retained the rounded corners and friendly fascia of its 1950s namesake, and added retro notes inspired by the streamlining of US streetcars.'

So what do you think. Is Heatherwick's answer to the Routemaster a design classic in the making?