Have to chime in here as I've lived in Merchandise for 12 years, and currently occupy the ground floor corner unit directly across from this construction site (old Esso station). I've lived in 2 units in this building. I'm also the President of the Board of Directors for TSCC 1565 (Phase 5), so have some inside information about the history and inner-workings of this building.
The layouts are generally pretty horrible imo. The interior design when they converted this building was done by Ryerson students to save money - and most units feel like a school project gone wrong. Most fixtures have fallen apart, bathtubs leak and have to be replaced, and overall construction quality (by Eastern Construction) was shocking. We gutted our 3 bedroom to rethink the whole layout, and found utterly stunning construction methods - the metal studs holding the inner walls together weren't bound together so they just flopped around once the drywall was removed. Tim Horton's cups and other garbage was thrown into wall cavities by workers. Insulation between ceiling slabs in hot areas like the boiler rooms was omitted, allowing heat to pass through units. Eastern really rushed the job, clearly.
That said, I've never had an issue with insulation between units. I have a music production studio in one of my bedrooms and never once had a noise complaint. I've lived in many condos in Toronto, most of which had paper thin walls - this building however, that is not the case. Some walls are thick 100-year old concrete that is hard to even drill into. I'd say it's probably some of the best material for sound insulation between rooms I've ever seen/heard.