McDonald's is opening its first US-based McCafe this week in downtown Chicago. After enjoying success with the concept abroad, the fast-food giant hopes to win over some of the US' gourmet coffee crowd from Starbucks. If the concept works, hundreds more US McCafes could follow, helping boost flagging fast-food growth. But there's a danger the young, trendy target audience will associate McDonalds too closely with burgers and fries.