Caroline's airy loft is just as described. It is bright with street noise, so as she says - it may not be for you if dark and quiet is required for sleep.
There was some major construction going on across the street and they started pretty early with significant loud dump truck banging.
We stayed in the city until pretty late most nights, getting back around midnight. The building and neighborhood were quiet.
We used Metro at all hours and never felt unsafe. It is a quick walk to catch the 6 and you can connect to anywhere you need. Yes, South Bronx is an underprivileged and underserved area so there is more litter and less attention given to the neighborhood maintenance. This neighborhood seems to be changing - new housing being built and an increase in neighborhood stores/shops. An up and coming area with lots to explore.