It looks like it’s just a pre-paid card — like a pre-paid phone card, your uni card, etc. You put a sum of money on the card (10 to 50 British pounds) plus pay a 2 pound “activation fee.” You then use it for local transportation — buses, trams, the tube, national rail services in the London area. When you use it for public transit you touch your card to the yellow reader on the bus or at the turnstile and it automatically deducts the cost of the ride from the balance on your card. You can add money to the card at numerous locations if you want/need to.

The big advantage is convenience — not needing change for the bus, not having to buy a ticket every time you take the tube. It’s also “automatic,” If you travel at non-peak times you get non-peak pricing. If you take so many tube and bus rides in one day that a one day travel pass would save money it deducts the price of a one day travel pass instead of the total of all your different trips.

Whether or not it’s worth it financially depends on your specific plans — how long you’re in London, where (which travel zone) you’re staying, how many places you intend to visit, how much walking you plan to do, whether or not you’ll be taking a tour or a hop on/hop off tour. I don’t think I used 12 GB pounds (cheapest card + activation fee, $18.50 US) worth of transportation in 3 days, so the cost wouldn’t have been worth it financially for me.

Thanks for clearing that up for me. I plan on spending six days in central London. So far I don’t think I’ll really be venturing out of the circle of places I plan on seeing. I don’t really know what else there is to see in other areas of London. On the top of my list is Westminster Abbey, Tower of London (but not a tour), Old Bailey, London Eye, Hyde Park, Globe Theater, Big Ben and some other places in between the ones I’ve mentioned.

I recently bought them for the sake of convenience since I’ll be part of a group of five who’ll be in London for four days. The cards arrived here in California less than a week.

If you fly into London and can use the card to get from the airport to town (or vise versa if you’re flying out of London), or will be traveling around in London for 4 or 5 days it would probably be a good investment for the convenience. I doubt you’d make back the activation fee in cost savings, but if you used 10 GBP worth of transit, the convenience would be worth it.

If you arrive and leave by train and are staying somewhere fairly central you might not use 10 GBP worth of transportation in 4 days so would waste part of the price of the card besides the activation fee. If you’re out of town on a day trip for one day (not sure how the National Rail part works) and on the hop on/hop off bus for another, you’re unlikely to use that much public transportation in another 2 days.

Yeah, we will be using the tube to get from Heathrow into London. If our cards still have a few quid on them when we leave London I won’t mind. The convenience of not having to buy tickets every time we use the tube is worth it to me, especially when you combine my uncanny ability to be out of cash whenever I really need it with automatic ticket machines becoming increasingly fussy about American credit & debit cards

Thanks for all the help! It’s still over a year before I actually make my trip, but I’m kinda thinking an Oyster card would be a good decision!

Yeah I was in London for 5 days a couple years ago, and I can’t recommend the Oyster card enough. They’re easy to get (just go to any ticket info window in a London train station—and there are several ) and you can use them for practically anything. You just swipe it against the thingey as you enter the tube and you can get to basically anywhere in the city