Some suggestions:
A fairly new place i dined at recently - Viand. 155 E. Ontario. Eclectic and very good tapas (as well as larger entrees) - every dish we had, and we were a large group of almost 10 people by the end of the evening, was very good - and a few were phenomenonal. Of special note, the coffee flavored grilled steak - almost mole like in flavor was quite amazingly good. The whole roasted Chicken entree was huge and also quite a hit at the table - even the cheese grits were popular.
For quick food on the go, say while shopping, Wao Bao in the lobby of Water Tower is one of my current favorites - and a place that I hope will take off as a new chain spinoff of Lettuce Entertain You. Very reasonably priced "Baos" (Chinese steamed buns) filled with a variety of fillings - tasty and manageable prices, fast service, and overall a great new fast food concept (with a lot more flavor than most).
Le Colonial - on Rush Street. Sure it is a semi-chain (others in other cities). but it is also a place where I have never been disappointed and always enjoyed the food. Upscale Vietnamese. In better weather I always suggest asking for the balcony.
Dublins. On State, just south of where it runs into Rush St. Open until 4am, 365 nights a week, this is one of the hidden secrets of good dining in the area. Their food is quite good - I almost always get one of their salads (like the steak salad a lot). Good food, serving late into the evening.
3rd Coast Cafe - on Dearborn and Goethe (just north of Division, so a bit of a walk, but very manageable from Michigan Ave). This is one of my long time favorite spots in Chicago (full disclosure, as a regular for over 10 years I know many of the staff and all of the owners). A great cafe/wine bar, open until 2am most nights, later on the weekend. Their daily specials are always good, anything with their bacon is a safe bet as well (the bacon costs them about $0.50/slice - super premium and very very good). Their crab cakes are good and they will hand-toss a pizza for you as well. Plus they have a great wine list of smaller wineries (buy a bottle and they give you a free appetizer), good coffee, and a full bar. Definitely one of my favorite spots in the area.
On Michigan Ave itself, closer to the Loop I am a fan of Bandera. Again, this is a chain, but I consider it quite a good one - tasty food and a good location.
Heaven on Seven at 600 N. Michigan (around back, same entrance as the movie theater) is another great option right off of Michigan ave. Good, cajun food - a large menu with not every dish being great but lots are quite good.
I'm also a fan, in limited doses, of Cheesecake factory (and I suspect their other restaurant Une Grand Cafe). Yes, it is a chain, and yes it is a tourist trap, large, and always crowded - but the food is, in face, quite good. With careful ordering it can be managed without extreme over eating (basically almost literally order half as much as you would at any other restaurant - i.e. one small salad for 2-4 people etc.) I generally get their small salad, perhaps an appetizer, and a slice of cheesecake - usually with leftovers if dining alone, or even if that is split with one other person. It can often be the case that if you don't want to wait you can go right into their bar and sit down immediately - always worth checking. But I would generally only suggest it for larger groups with some people who are not too adventurous.
Shannon