We have stayed for a week in July 2017 - 2 families with 2 kids each. The four bedrooms were perfect for us and it worked out very well. The apartment is a generous size and it is in a perfect spot. Easy walk to the ferry and to the town center. We did pay extra for parking in the building as there is no free parking anywhere nearby and it was very convenient. There is a grocery store across the street that carries the basics, if you want a better selection another one is about a mile down the road. Lots of cafes and restaurants nearby.
Only one of the bedrooms (the biggest one) has an A/C so the other rooms do get a little hot in the summer heat - but if you put the bedroom A/C and the two other A/Cs in the living room on and opened the doors before going to bed it was bearable. It has a small but functional kitchen space - we usually used it to make breakfast and sometimes a quick dinner. It did have some basics already there which was nice - salt, pepper, olive oil, vinegar etc. The dishwasher detergent and laundry detergent was also provided.
We loved sitting on the balcony in the morning and in the evening, so serene.
The owner, Mary, is fantastic. Very responsive and helpful. She was waiting for us when we arrived and also had two mini bottles of local wine for us, very sweet and much needed after a long drive. She also provided us with some tips for restaurants and other stuff to do.
The best part, of course, is the lake itself - Lago di Garda is beautiful. We have actually travelled all around the lake and would highly recommend that as the north is quite different than the south. We also took the kids to Gardaland and Caneva water park, they loved both and it was an easy drive from Desenzano.
The internet was very good and reliable, worked reasonably well even when more than one device was connected.
Overall, it was an amazing vacation.