I visited Venice with my mom, brother, and 2 aunts and we were very comfortable in Mario's flat! The location could not be more central, just steps away from Piazza San Marco. The apartment is furnished with modern amenities and looks just like the photos. Wifi worked well and the air conditioners in each room were great. I mostly communicated with Paolo who was very prompt and timely with check-in. The only thing to mention is that one of the bedrooms has 2 small beds, one of which is a cot so I'm not sure how comfortable that would be (none of my family members used it to sleep) but for 5 of us we were very comfortable.
Would highly recommend!