E-tickets are 100% the way forward. Compatible across devices, can be booked online in the comfort of your own home/workplace/etc, significantly easier to detect and reduce ticket fraud, provides lots of lovely data to monitor travel patterns and whatnot, reduction in retail time, freeing up ticket offices and other retail staff to worry about complicated tickets and those customers who need extra assistance.
Probably the only way it could be improved is a little electronic kiosk at the station that if you're having a disaster and can't view your ticket (lost phone and no access to your computer etc) then you could tap in your details and print out a copy of the barcode, perhaps for a nominal fee to cover the cost of providing the machine and the receipt roll etc.