I never used one. Never planned on it. I keep hearing people complaining though that they will charge you something like $25+ for a $7 meal. That is insane!
I get that it is convenient and all but at that point, it would be cheaper and faster all around to just go pick up the food yourself.
It is bad enough that most prices of food have gone up when it comes to eating out. I remember when my veggie bowl from Chipotle was $5.99 and now it is over $8. I still remember $5 footlongs from Subway. Heck, when I was growing up, they had 50-cent burgers at Mcdonald's, remember those? lol