The many, many upsides:
This is a perfect spot for 1-2 people! The small apartment has been carefully and thoughtfully appointed, and every inch has been maximized. The bed is excellent (I have back issues, so this was a MUST for us), the sitting area is cozy, and the rain shower head is divine. We were in Chicago on one of the hottest weekends of the summer, and the apartment stayed cool and comfortable.
We appreciated the snacks and bottled water, the well-stocked toiletry supplies in case we'd forgotten something, and the wide selections of coffees, teas, and espresso. The backyard garden is a flower-filled oasis, and the hosts' sweet little pup will charm you.
The hosts are incredibly communicative and helpful. Definitely plan to join them for a house tour and a cup of coffee/glass of wine!
The close proximity to the Blue line was GREAT for getting downtown. The hosts sat down with us to look at a map and helped us figure out the best way to get to where we were going. AND they offer parking passes, in case you want to park your car on the street for a few hours after check-out.
The very few downsides:
First, if you are a light sleeper, have excellent hearing, and/or want to sleep in past 6 or 7 am, plan to bring ear plugs. The apartment is in the basement level of an old house, and the floors overhead are very, very creaky. You'll hear every footstep, puppy scamper, and scrape of chair leg. Unfortunately we weren't able to sleep well because of this. That said, we would stay here again, but we'd want to bring ear plugs. (A white noise machine would work, as well.)
Second (and this is minor), the bathroom is not very private -- the door to the toilet/shower doesn't close all the way, and the sink is in the bedroom area. This was not an issue for us, but if I were traveling with a work colleague or someone I didn't know very well, the lack of bathroom privacy would be a minor downside.