My girlfriend and I (we're from Boston) just spent 5 nights in Chicago. I'm definitely the planner of the group and did a lot of research on Chowhound before we made our restaurant plans, and I couldn't be more thankful for all of the advice on this board. I thought it would be worthwhile to let you know how it went...
For breakfast, the surprise hit was Orange down on Harrison. The place had a great laid back vibe, and our eggs were amazing. We spent the entire breakfast talking about how we could open a place like this in Boston. I even picked up a package of their orange infused coffee...I wasn't expecting to like it, but it was delicious. We made the obligatory House of Pancakes trip which didn't let us down. Lunch was relatively uneventful, but we had a pretty good meal at Bistro 110 - high marks to their quiche, even if the location is a bit touristy.
Onto the good stuff...
Avenues - a great meal, if a somewhat sterile atmosphere. It didn't help that there was literally like one other couple in the restaurant with us on a Tuesday. The service was attentive though, and they even seemed to loosen up a bit since we were a bit younger. We did the 10 course "Palate" menu since we're both not big fans of caviar and lobster (which is odd, as we're from Boston) and the food didn't disappoint - we had selected Avenues because while we wanted to be a bit experiental, we didn't want the exoticness of Moto or the more classic setting of Everest. Favorites included a BBQ pork belly and lemon gazpacho - her favorites were a tuna with olive tapenade and beet salad. They complemented the meal with a small puffed cheese amouse bouche and some small chocolates afterwards. Overall, I thought they included perhaps one too many vegetable courses and could have gone with another fish...but that's a minor quibble. My homework disappointed in one respect though in that I didn't realize they don't do a wine pairing. Overall, with tip and wine, the meal was just under $600, and while a very memorable experience, it was not our favorite restaurant of the trip considering the cost.
One SixtyBlue - this was the hit. Great atmosphere and bar area from the minute we walked inside. We were surprised that it wasn't crowded/packed, considering it was about 8pm on Thursday. It may have to do with the location, which is a bit out of the way and made it more difficult to catch a cab home later in the evening. Our waiter was great - very interactive and made great recommendations based on our tastes. Typically we might have been put off by this a bit, but it worked in this setting. We started out with a goat cheese appetizer at his suggestion, and then moved onto seared scallops and a vegetable gnocchi. Her gnocchi was delcious - I don't think I've ever had any that were so light. I had the pork tenderloin as my main course which was perfectly tender, and she had a Rib Eye steak. My pork was telicious, although it was accompanied by a pork belly which was a bit chewy. Her steak was a bit neutral (ie, cooked perfectly, but could have used a bit more seasoning), but was accompanied by delicious potatoes that made up for it. The bread pudding for desert was just right. The wine list was comprehensive and not very pricey.
MK - A good experience, but for some reason not as memorable. The space is more cavernous and not as intimate as One SixtyBlue. We had an 8:30 reservation on Friday and the place was packed, although several tables opened and were not reseated immediately after we arrived. Our waiter shared the serving responsibility with another which made it a bit confusing. I started with an octupus which was a bit overcooked and had too much of a smokey taste to be truly enjoyable. However, her corn chowder was delcious - it was poured at the table with some small lobster pieces. Our main courses were bison and duck - the bison was great, perhaps the best meat dish of the entire trip, but her duck was chewy and she didn't finish it. Desert was the Cake and Shake at the recommendation of our waiter and finished the meal nicely. We found the wine menu to be quite pricey and had to look harder for a good value.
Both meals at One SixtyBlue and MK were just under $350, and we agreed that for the quality of the food and the price we paid, we enjoyed those experiences more then Avenues. However, we were extremely impressed with Chicago's culinary scene (and the city overall!) and were sorry to leave :-) Thanks for all of the recommendations!