I think that the NHS e-Referral Service really tightens up the whole process of booking a hospital appointment, because you or your doctor can book an appointment instantly.
With the old paper system, you would have to wait for a referral letter and then another 6 to 8 weeks before you got any details of the appointment through from the hospital. You could then chase up the hospital, only to be told that they hadn't received the referral in the first place. The electronic system immediately removes that dead time and stops referrals falling through the net.
My GP needed to refer me to the hospital, so we discussed the clinics that were available at different hospitals and agreed which would be the best and most convenient one for me. Dr Miller booked that appointment for me there and then using the NHS e-Referral Service.
On another occasion, I knew where I wanted to go and my GP just provided me with an access code, so that I could go away and book the appointment online myself. It's also really useful to see information about the waiting times at different hospitals, because you may choose to travel a bit further in order to get a quicker appointment.