The loft space is wonderful; very large and quite bright. It's an old industrial space, which makes it very cool; it's got the 'wow factor'. Comfortable bed, well equipped kitchen and full bathroom (including tiny little washing machine). For a reasonable price Doris the cleaning lady comes once every week/two weeks and keeps things clean. Location is very good near old Carouge and Plainpalais (restaurants, shops, bars abound) and well connected with public transportation links. Well located to go for runs along the river, too!
Hosts were accommodating, allowing me to drop my luggage a day early as I was sent on an unexpected business trip the day I was supposed to move in.
The reason I'm only giving 3 stars is some 'intangibles' surrounding my stay; there was a lot of noise from parties the hosts were throwing as well as construction, and I was asked to provide access to the apartment on very short notice a few times to allow people to come and see it (for non-urgent reasons). I felt uncomfortable complaining about the noise (nobody wants to be the annoying neighbour), and I never really felt 'home' as there was a bit too much access by others.
In short, I would absolutely recommend the apartment for a stay of a week or two, but my two month stay was on the long side.