OK, I will say that I have some hesitancy posting this topic on this site, since I know that most of you are "steam guys", but here goes - and apologies for the length:
I've been obtaining quotes for some pretty extensive plumbing work for our 144-year-old farmhouse (1876), non-air-conditioned NJ farmhouse, which currently includes replacement of the existing steam boiler with a hot water loop for some limited areas served by baseboards. On recommendation from this site, I've got a pretty comprehensive quote from Ezzy T. (thanks, guys).
In the interim, I've had a couple of conversations with some fellow architects and MEP consultants I work with, who are almost universally saying, "Why are you replacing your steam boiler? You should just replace the entire heating system with a VRF system. It's far more efficient, would give you both zone-able heating and cooling, is less fussy to maintain, you wouldn't need to certify and potentially re-line your chimney, etc.". I should add that I'm a LEED AP, so I know that from a standpoint of efficiency and sustainability, it's probably what I SHOULD do.
My wife and I LIKE the comfort of the steam heat, and I had always considered simply replacing the boiler, and maybe at some point, adding some mini-splits (certainly a more costly approach, and doesn't take full advantage of the heat pump capabilities). That said, I do have to agree that the VRF argument is fairly compelling, which now has me second-guessing my original approach. I have dropped gyp bd ceilings hung below the original ornate plaster ceilings in most 1st floor rooms, as well as accessible attic and basement spaces - so running refrigerant lines wouldn't need to be all that invasive. The exterior walls are NOT insulated (another major project) but I anticipate that I will address that at some future point.
Regardless of whether or not I replace the boiler, I've still got extensive plumbing work to do.
So, I guess the question I'm asking you steam experts is, if it was YOUR house, what would YOU do?