The Return to Quest NPC feature is awesome, I really enjoy it.
I found out that if I have a quest ready to complete, I can travel back to town (to sell items, use the blacksmith, or level attributes) and then use the Return to Quest to travel back to the location I was, completely free of charge. I don’t know if this is intended since there is a charge for traveling to areas normally, but maybe Return to Quest NPC shouldn’t work if you’re not in the same zone as your NPC.