The Conrad is my home away from home
I've been a regular at the Conrad now for about two years. I stay here 3-6 nights every month. The reason I come back is that the Conrad is, quite simply, the finest hotel in the best location in its price category. 
Service
I cannot say enough about the service here. All of the staff, from doormen, to front desk to housekeeping are responsive and helpful. When making a request for anything from room details to restaurant reservations, I've never once been told "that's not my job" or "please see the concierge". The staff here all make an effort to get to know their customers, even remembering names. The more you stay here, the more they get to really know you and the more personal the service. 
Rooms
I've stayed in just all all categories of rooms. The basic rooms are all well appointed, clean and quite large. I would describe the accommodations as being in the "International Business Class" category. The interior facing rooms can be a little dark, so it might be worth the upgrade for a street facing room if that's important to you. The other upgrade, to a suite, provides a generous amount of space. I've even stayed in a terrace suite which, unbelievably has a private terrace facing Michigan Avenue. You could hang out and have mojitos on your own private terrace. An amazing option, if you're so inclined. 
Restaurants
The Terrace bar at the Conrad is a major outdoor hotspot on warm nights. In fact, get there early or get your name on the list since the wait on a weekend night for a table outside can be lengthy. This is one of my favorite roof-top bars, period. It's low-key, which makes it really desirable. The food at the hotel is also terrific. I strongly recommend the breakfast quesadilla. 
Health Club
This is important to me since I travel a lot. The Conrad is currently renovating the gym and it is time for an upgrade. I hope to offer up a review of that in the near future. I don't think there's a pool. While there is no spa, the Nordstrom Spa is one elevator ride away.
Location
The hotel connects directly to the Nordstrom shopping mall and on to Michigan Avenue. It's dangerously convenient. On the other hand, if you forget a belt, shoes or something else, having Nordstrom right there is hard to beat. 
Here's a tip: the best shoe-shine in Chicago is inside Nordstrom near the Men's shoe department. Tip generously - they only charge about $3.