I love that it provides nutritional facts. Very few other services like this provide that (looking at you, Instacart).
@gaganbiyani recently launched Sprig (eatsprig.com), shared a few days ago on here - http://www.producthunt.co/posts/83
I use Sprig, Munchery and Zesty. Zesty is probably the one that I use most; I think I'm the no.3 user (last time I checked). I love that it displays the nutritional information - that for me is the key reason that I use it.