The senior (over 60) version is very good value. If doing a day return from say Derby to Sheffield or stations beyond, it is cheaper to use a senior Wayfarer for the Derby-Sheffield leg. You don't need an over-60s railcard to buy one, although you may need some other means of proving your age. They can be used all day on buses, even before 9 am. They can only be used on trains after 9 am on weekdays, but in some cases this may mean that you can use a Wayfarer before off-peak fares are available.
Earlier this year, I was unable to purchase one before boarding the train at my unstaffed EMT station. When I explained the situation to the EMT guard, I was expecting him to tell me to buy one when I changed trains at Derby, but instead he sold me one on his ticket machine, on standard orange card. I think the wording on the Wayfarer website may have been overtaken by the modern on-train ticket-issuing systems that can issue them.
In the past, when I have bought Wayfarers from Derby station, they have been printed on orange card which is then sealed in a Wayfarer wrapper. Again, the Wayfarer web-site says that you can only buy tickets on the day of travel, but I had no problem buying one for a future date. The versions sold at ticket offices have no scratch-off date - the date is printed on the orange card ticket, so be careful to tell the clerk if you want it for a future date. The guard didn't have a Wayfarer wrapper to put the ticket in, but it was accepted without any problem on subsequent bus journeys.