The big change for 2010 is that you can now use Oyster pay as you go on National Rail. This is a good thing, but it's not perfect. The main advantages of Oyster PAYG are price and speed. For instance, a single bus ticket in 2009 cost £1 on Oyster or £2 in cash, so it's better for the individual to use Oyster. Meanwhile, if I'm on the bus and there's a line of people getting on, I've noticed that it's a lot quicker for everyone to walk past and bleep their card rather than having to fumble around for coins, so Oyster benefits all the other passengers as well.
On the tube, you can extend a travelcard. For instance, suppose that I have a travelcard for zones 1-2, and then I travel from zone 1 to zone 3. As long as I swipe in and out, I'll just get charged for the zone 2 to zone 3 journey, which is cheaper than zone 1 to zone 3. However, this gets a bit more complicated on National Rail, as described at the London Reconnections blog. Basically, you have to get an Oyster Extension Permit in a situation like this: it's free, but you still have to queue up at the ticket office for it. That's obviously slower than just swiping your card at the barrier, and you still have to swipe anyway.
The other issue is that you can't put a rail season ticket onto an Oyster card; that still requires a paper ticket. In my case, I have a season ticket between Norbury and Willesden Junction (rather than a zone based travelcard). Now, suppose that I want to travel to East Croydon. If I swipe in at Willesden Junction and swipe out at East Croydon, I'll be charged for the entire journey, even though part of it is already covered by my season ticket. I could buy a paper ticket at Willesden Junction (from Norbury to East Croydon), but I can't do that with Oyster. So, that means that I need to get off the train at Norbury, go out through the ticket barriers with my paper season ticket, then come back in through the barriers using my Oyster card, and wait for the next train. On this route, all the faffing around will add 15 minutes to my journey (taking the slow trains), and it means that I can't take the fast train from Clapham Junction to East Croydon.
The good news is that Oyster fares are a bit cheaper than cash fares. In 2009, off-peak journeys cost £2.60 from Norbury to East Croydon, or £3.00 from Clapham Junction to East Croydon. In 2010, the Oyster fares are:
|Willesden Junction to East Croydon||£2.70||£2.00|
|Clapham Junction to East Croydon||£2.70||£2.00|
|Norbury to East Croydon||£2.20||£1.70|
Previously "off-peak" was any time after 09:30, but now there are two peak times: 06:30-09:00 and 16:00-19:00. That's understandable, and it's similar to the rules for unfolded bikes on trains. Anyway, the simplest approach for me is to swipe in at Willesden Junction and ignore my season ticket. At peak times that will be 10p more expensive than the old cash fare (which I can live with), and at off-peak times it will be 60p cheaper. It would be nice to pay the "real" fare, but at the moment it's not worth the hassle.