We've been to HyVee Market Grille several times at this point, mostly for brunch but a couple times for dinner as well.
The food, the service, and everything else overall is pretty average -- nothing really stands out as amazing or horrible. For brunch, you can order off the menu, but they also have a buffet option, too. The buffet food is, in my opinion, noticeably worse than ordering off the menu but I think that's to be expected.
I do appreciate the convenience of being able to get groceries afterwards, the reasonable amount of variety, and that the menu has some nutritional information for some of the items though.