JSM was awesome to rent from! We lived in one of their multi-unit facilities on Johnson St. with the office in the building for 3 years. Our property manager's name was Matt and he was amazing! I'm not sure how much that differs from other locations in terms of service and attention, but we had a great experience. They responded to every maintenance request promptly (sometimes I even had to ask them to wait a day or two!) and their maintenance workers were very polite, incredibly clean and charming to talk with. I even subleased our apartment for the last few months and the process was smooth like butter.
The only downside is that it was pretty expensive for what it was. (Granted, Madison is out of control expensive! Especially downtown during the time we lived there.) It was a "garden level" one bedroom apartment and a little dark. From 2014-2017 rental years we paid almost 800 per month. The actual area of the apartment was about 550 square feet, which is really pretty small for two people (about the size of a large studio). It didn't have much by the way of amenities, there was a dishwasher and laundry in the building. But, there was no balcony or other outside space to enjoy.
All that aside, I would definitely rent from them again and highly recommend them above and beyond other management companies I rented from during my 9ish years in Madison!