FO3 Nexus is a modding site, a warning on it is VERY appropriate as this affects virtually ALL mods.
But that's not exactly right in context. It cannot be critically affecting all mods because I'm running a pile of them and I'm mostly fine. MMM-Increased-Spawns, MMM-Zones-Respawn, Phalanx 0.96, fellout, greenerworld, Foes Reworked, and others.
The truth is that it depends on which mods someone has loaded. I feel like its overkill to make the claim be so broad as to say virtually all, and so on.
After I made a few changes to Phalanx, I stopped ALL crashing in my savegames - - my own mod was the only one causing crashes in my line-up. The one problem that persists is the skin color issue and I know what I can do to fix it in the future, assuming they don't (that one, they might really want to look at, if nothing else).
If any sort of advisory were made like that, I feel like it should reflect the fact. That fact being, some mods will cause crashes with it, some won't, and the user should decide what to do based upon that.
edit: 1.5 fixes more for me than it breaks. I would have been unappreciative if someone had "warned" me, saying, "do not update to 1.5, it's bad!!!!"