They were heated either by hot water boilers and radiators (a good sign) or by what are called gravity furnaces (a bad sign). 

My big one is that the bathroom is in the basement, so the first thing is to figure out if i need to pump the sewage against gravity :(

Then, the person has to hold the filter in place with one hand while holding the filter in place, closing the filter door and trying to get the screws back in, or try to get those difficult sliding locks to line up while gravity is trying to pull the filter down, pull the door down and pull the amateur down off the ladder.

So dont know if your proposed improvements are on sloped or level land or some pretty steep land with cuts and fills and deep sewer to make gravity flow. 

I had the enormous "octopus" gravity heater in the basement which had asbestos wrapped around its ducts.

First one was a random 3- decker condo someone had added a 4th floor in law to in defiance of gravity and common sense.

We have accidentally flipped a few places and thought "hmmm... well, maybe since gravity is pulling us in this direction, maybe we should just go with the flow?"

I had a sewer inspection to confirm the gravity of the issue ($7000 sewer job awaited us) and negotiated back down.

Plus, just like @Jamie Rose said, as long as you can open a window it's very rare to get too hot for people.I haven't yet closed on my first property, so maybe my opinion doesn't have a whole lot of gravity.

I have found them to be useful with the expectations that they're definitely going to find problems, it is a matter of the gravity of those issues and how you plan to handle them.