Erwin's is a great place for an upscale dinner, without the touristy fanfare of downtown Chicago. The best part about this place is the brunch. With so many decent "diners" in the city, I don't always think it's worth the money for a nice brunch, but this place sure is.
Also, if you get there before 7:00 on a weekend, don't bother paying for valet. Take the 5 minutes to look for a parking spot on the street. They are generally pretty easy to find.