In terms of being a customer I have an awful lot of time for the Royal Mail currently, to send letters/small parcels I find the rates perfectly reasonable, there's an accountability to the rounds that means I've only ever found workers to be conscientious. If a parcel can't be delivered you can go to the office when convenient or get it re-delivered elsewhere easily enough.
Contrast this with every experience I've had of the couriers utilised by companies like Amazon and when sorting out a Passport...things get left in broad daylight, in the rain, drivers have been completely disingenuous and claimed signatures which weren't given, if you're out they will only organise a redelivery between 9-5 on a weekday. I appreciate this is purely anecdotal but I have an awful lot of time for the RM (declaring bias here my Dad is a postie of >20yrs).
In terms of the more general point about the efficiency of privatisation - I'm relatively on the fence about it. Although, Ewan, your graph about the rail companies is just the worst kind of statistical misrepresentation.
Given the problems with the pension contributions of workers I think there's a distinctly immoral aspect to shifting the company on. If there's a looming pension deficit due to mismanagement whilst within the government's purview then it's their responsibility to ensure that is resolved. Also Royal Mail, I believe, have suffered significantly as a result of the 2006 Postcomm decision to encourage competition because it's half baked and the 'Downstream access' princple means a courier can go and pick up a load of mail from a company, drive over to a Royal Mail office (who are obligated to deliver it) and dump it on them having negotiated middle-man rates.
I appreciate this is an age old/anecdotal argument but isn't the transport system in, say, Berlin a PLC owned by the state? Because that travel network is beyond reproach.
"Give me a prejudice, and I will move the world"