We stayed in a 2-bedroom City Stay apartment in Lindenstrasse in August. I highly recommend it. The apartment was very clean (it seemed brand new), well-appointed, and with many amenities one needs. The bathroom is fabulous with separate shower and a bathtub. I loved the big drawers under the sink. There were fans in each of the bedrooms, which are essential in the summer.
The location is fantastic. In the very nice Seefeld neighborhood a few blocks to the lake and the promenade. We enjoyed swimming at Strandbad Tiefenbrunnen and walking to get gelati from Gelati am See after dinner.
City Staff were excellent. Very responsive and helpful. They set up a very nice pack-and-play (portable crib) for our youngest daughter before our arrival. They also allowed us to keep our luggage in the locked storage room after our stay as we toured around Switzerland.
Note: we stayed in the City Stay both at Lindenstrasse and Kieselgasse. I recommend Lindenstrasse as the rooms are newer and it is quieter and cooler than Kieselgasse. (But if no choice, Kieselgasse is also a great option).