http://uk.reuters.com/article/2010/07/30/uk-britain-bikes-idUKTRE66T2M520100730

Same as Paris Vélib: basic subscription/payment, and free for the first half-hour, except it's £1 for a day in London, and €1 in Paris. The bikes themselves are very similar - basic heavy three-speed type, only a very small space to carry a single small bag or parcel.

Cycle path provision is as patchy as it is in Paris, and you need at least as much road sense and awareness as you would if you were driving, and probably more. Please don't think of it as a "fun" leisure activity, more a self-powered taxi to get you from A to B.

There are very varying reports about non-UK credit cards (including other European chipped cards) actually working with the bikes. Actually, the overwhelming majority of reports I've read about non-UK cards report failure, though even that doesn't seem 100% predictable.

There might be work-rounds involving pre-registering on the TfL site, but it looks as if you can't rely on just turning up with your card and borissing (it should be really kenning, since the development work was all done under the newt man's regime) away.

>>borissing<<

That - to me - would rather recall:

http://www.newyorker.com/online/blogs/lauren-collins/2012/08/dangle-boris.html

After seeing how traffic here in London treats bike road-users, I personally would be very reluctant to use them. Tourists on them look very stressed out, unless they are riding through the big parks.
I wouldn't count on getting access to one either, the stalls around tourist venues are almost always empty.

there are some "apps" which can tell you which bike racks have bikes. These are linked via GPS and easy to find on t'internet so you can more easily get a ride.

I use them whenever I am in London. They are decent city bikes, and very well maintained. Never had a problem with my non-UK Visa card...though of course it should be of the chip and pin variety, which are still hard to come by in America (I suggest you get a chip and pin for London anyway, as you will find it hard to pay your way along with the old type at various cash points). If you are an experiencied city bike user you should be ok...but London is no city to learn city biking in. I find that drivers in general tend to respect bikers as long as they observe the rules. In fact I find it easier to ride there than in my country. You do see a load of idiots trying to ride a Boris bike though...please don't be one of them. If you know how to ride a bike well in a busy city, I encourage you to use them. There is a Barclays Bike (their official name) app on Android and possibly also on yukk iphone which shows you all the nearest stands with teh no of bikes available and the no of empties - just as important when you come to return of course. It also shows you your route and position via GPS - very cool. The aim is to use these for short trips from A to B, so the first 30mins are free but hire fees shoot up exponentially after that. You need to allow 5 mins between returning and renting. And you need to press the code in hard. Last bit of advice: make sure the bike is secure when you return it, or you may get a heavy bill on your card otherwise (lift it up from the saddle to check it won't come off the stand).

It's worth pointing out that UK newspapers are going through a "London's unfair to cyclists" obsession at the moment, to a point where almost any accident involving a cyclist is reported as the sacrifice of an innocent martyr to self-centred killer drivers.

In spite of this, I've not seen a single report of an accident involving a Boris bike. The bikes are designed to be visible, and I suspect that nervous tourists on them are less at risk (in a city where drivers tend to be very, very disciplined and aware of what they're doing) than lycra-clad locals with attitude, a sense of victimised entitlement and a meeting or hot date to get to.

I've lost count of how often as a pedestrian my health's been threatened by one of them. I've never encountered a Boris biker, however ill at ease, riding in a way than endangered other road users.