Burr Ridge/Willowbrook Area
There is not much in Burr Ridge or Willowbrook. I've heard great things about Courtright's though I've never had the pleasure of dining there. Your best bet for steaks would be the Westchester branch of Morton's. It is only about 8 or 10 miles from where you'd be staying(about a 20 minute drive) It's a top notch steakhouse if you've never been to one of their many outlets. I haven't had too much luck with suburban Sushi. Vie Restaurant in Western Springs is another option for fine dining. As for lunch, The Country House has always been a favorite. They serve great burgers in an old, woody bar setting. Another lunch alternative would be Salbute in Hinsdale. They serve upscale Mexican fare. One final lunch suggestion is Bobak's buffet in Burr Ridge. They specialize in Polish staples such as pork tenderloin, dumplings, sauerkraut and the like.
Country House: http://www.burgerone.com/
I saw this post a little earlier and also immediately thought of Courtright's. I work in Burr Ridge and there's really not anything in the immediate area that I would recommend.
For sushi, you might try Yokohama in Westmont. I haven't been there in a few years, but it was always decent food & good service. Depending on where you'll be staying, you may want to try downtown LaGrange for some interesting options.