Surprisingly I don't think we are in real disagreement, it depends on the requirement. He said he faced problems along the way and you will if you directly substitute NiFe for lead acid.
There are some nice features, survival frozen and discharged may be vital in Siberia, I can't see it being needed in the UK, lead acid will cope with temperatures here unless left flat in which case they die anyway.
Being able to discharge to 100% is nice, you won't be able to do that without special inverters and control gear. The ability to use less capacity comes at an enormous price for the nominal capacity.
Surviving over charge and not needing a charge controller is a virtue, if your loads are basic and primitive ( incandescent or heaters) then fine. You will not be able to use the sort of loads that most people expect without some form of buck boost converter or tap changers.
The issue of changing electrolyte is valid, I think you have to do it to get long life, the thing that my friend found is that once damaged they don't respond to new electrolyte, The true Edisons may be different.
If survival alone is the aim then yes they look fine. In the old days before modern devices they would be heaven for surviving off grid, sadly none of us could afford them and those of us who got them used and cheap got some of the advantages but not others.
By all means try them, used properly I am sure they are better value for money if you are in for the long haul and deal with their limitations. If you are over 60 then it probably won't work out.
Flux