When Barclays Cycle Hire, London's newest mass transit initiative, celebrates its first birthday at the end of the month, its unmistakable bicycles will have crisscrossed the capital 6 million times. If the mayor of London, Boris Johnson, wanted to raise the profile of cycling then he has certainly succeeded – from the title sequence of The Apprentice to an endorsement from Arnold Schwarzenegger ("You can eat a few extra Wiener schnitzel and get away with it"), the so-called "Boris bikes" are impossible to miss. But has the scheme made a substantive difference to the lives of Londoners?

One of the pioneering journeys was made by an Australian web designer called Chris Skitch, from his office in Hoxton, east London to home off Trafalgar Square on a balmy Friday afternoon last July. Skitch had not cycled for 20 years but something about the scheme appealed and now he was bombing down Clerkenwell Road when he became aware of a surprising commotion. Workers, spilling out on to pavements outside pubs on that first day, began spontaneously clapping and then exuberantly cheering his progress.

"Before I started I was thinking, It's going to kill me. I'll be scared. I'm not fit enough," says Skitch, "but after that first ride I was like, Wow, I'm in love. You get off and you're buzzing, you feel like you can do anything."

Skitch set up the borisbikes.co.uk website – which is completely independent of the scheme's operators Transport for London (TFL) – and it has become an informal hub for the varied users of Boris bikes. One retired gentleman, who doesn't ride himself, has made it his mission to visit all 400 docking stations in the capital and take a photograph. Two riders launched the Boris Bike Challenge, a quest to swap their bikes at every single docking station in a 24-hour period, a distance of 100 miles. You could even go on a 30-minute "Boris bike date" with PJ Jones, a 26-year-old project manager.

A few people, of course, just use the bikes to get around. There are 6,000 bicycles in central London and they can be ridden by members or by casual users, who pay at a docking station with a credit or debit card. The set-up strongly incentivises short jaunts – the first 30 minutes of each trip are free – rather than all-day expeditions, which cost £50. Non-return of a bike incurs a punishment of £300, which might explain why only 12 have been stolen in the first year.

Another explanation is that the bikes are purposefully ugly, weighing a hefty 23kg and with the added indignity of being a mobile billboard for a financial institution. This suggestion received short shrift last week, however, at the summer picnic for Skitch's Boris Bike forum at All Hallows by the Tower church in the City. "I think they are very beautiful," says Martin Carr, a pastoral assistant who visits his congregation on the bikes. "I always want to say, if I'm on a Boris bike and next to another Boris bike: 'Nice bike.'"

Not everyone has retained their affection for the scheme. "It is a very good idea but in practice it is unusable," says Stephen Bayley, who was jury chair of the 2011 Brit Insurance Design awards, which actually gave Barclays Cycle Hire the transport prize. "I used it from nearly day one, but I gave up about three months ago when I had to go to nine different docking stations before I could park my bike, which took over an hour. It's not a reliable transit system for working people, it's an amusing curiosity for tourists."

This is a recurring complaint. The bikes make 20,000 journeys a day, but in a relentlessly predictable pattern, with huge spikes during the morning rush hour at the major rail stations and then again, in reverse, as commuters dash back to catch their evening trains. The largest terminal, at Waterloo station, can house 126 bikes, but TFL admits it could have five times as many and still not satisfy demand. More frustrating, as Bayley discovered, is when you successfully hire a bike but cannot find a place to return it at your destination.

On a tour of the nerve centre for Barclays Cycle Hire, near King's Cross, I raise the issue with Kulveer Ranger, Boris Johnson's director of environment and digital London. "It's true," he says. "We can't guarantee that you will be able to find a bike or be able to dock it. The bus network can carry 6.5 million people a day, the tube 4.5 million, but there are only a few thousand bikes, so not all Londoners are going to get them when they want them. If you have to make an urgent meeting, you've got to think, 'This scheme does not do it for me.' But it does work when I'm relaxed and I want to make a journey."

Ranger can point to some notable successes, not least the fact that there have been fewer than 100 accidents and none of them serious. But a residual concern remains who is using the scheme: overwhelmingly white men aged between 25 and 44, many of whom earn more than £50,000 a year. For a scheme that has already cost £79m, with a further £45m for the extension to cover the Olympic Park next year, can we really justify this "posh-boy toy"? "If you look at the normal demographic for cycling, it's exactly the same," says Ranger. "But that will change as we move into year two or three and we see people getting comfortable with it."

So, is London in the midst of a "cycling revolution"? The mayor would say yes, but others are more sceptical. "It just isn't a cycle-friendly city," says writer Will Self, a "bikie" who is mildly disdainful of Barclays Cycle Hire. "I sort of approve of the idea of using crap cyclists to slow down the traffic stream but it's a bit suicidal – like throwing people over the top in some conflict." One year on, however, and with nearly a million casual users of the scheme since December, it seems it is a battle that many are willing to join.