J.W. Marriott is a mid-to-high-end hotel in Chicago's downtown loop area. Very sparsely occupied in the morning hours, you'll likely encounter travelers and hotel guests with hotel staff more than any other workfrom-like executive/creative WiFi surfers.
Lobby Lounge offers free WiFi and outlets. The hotel is open 24hrs. Coffee is available between 6am - 10am, during hotel breakfast. The lobby bar opens around 11am - midnight. There are two main communal tables with plenty of outlets under the tabletop, but it may be "reserved" from time-to-time due to an event or function.
The environment is decidedly higher-end, even though the coffee prices are reasonable in the morning and the lounge is a decent drinking area in the afternoon and evening. In full-disclosure, the company I work within day-to-day has a hotel-based office here and does a lot of AV work for the events they hold. As an honest Workfrom.co-scout, I will still say it seems to be an okay place to get work done.
Because of the high-end feeling, you may find yourself adjusting your seating or trying to look like you are meeting another executive for an event or to take them on-the-town. With that said, most staff seem friendly and helpful toward the office-challenged. Their restaurant "The Florentine" has some of the best eggs in town — wife and I suggest the eggs-benedict or an omelet with fresh field greens and potatoes.
There's a server in that restaurant that is always a pleasure to see and she has greeted us kindly, even when we had our 1-year-old in tow. Only drawback to this location might be the "hotel smell" — where if you didn't notice, almost all hotels now pump-in a small amount of fragrance to make the place feel fresher and more pleasant — sometime people can be sensitive to it. A good choice if you want to feel like a savvy business traveler and enjoy the high-end for a day here in Chicago. Convenient to the Willis Tower, and Millennium park plus downtown shopping and the financial district here in Chicago.