Unless you're going for one of the grilled meats, Mantini's is probably not worth it.
What's to love?
The interior is nice. Open kitchen, good lighting, and a clean space with good table room.
What's not to love?
Well-intentioned but insufferably slow and spotty service. Almost nothing on the menu for vegetarians. The salads were anemic. There was nothing "wild" about the mushrooms in the wild mushroom quesadilla--more like "weird" mushrooms. The menu seemed lost, like someone was trying to squeeze together casual steakhouse and upscale American eclectic menus. And most everything seemed to be 10-20% overpriced.
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I will say that the majority of the people at the table got steaks and seemed pleased, so if that's what you're going for, then it's probably more like a 3 star experience.