Two major issues here:
1) I've used them twice, and the order has been wrong both times. Not horribly wrong, but mistakes.
2) They added an almost 25% driver tip after the fact, without my consent. Look, if you want customers to subsidize your drivers' wages, add an option to tip when you order online or have customers sign on delivery. NO ONE has cash to tip.
Next time, I'm using GrubHub or getting off my lazy ass and grabbing food myself.