First off, I buy a lot of Scrap Yards, Swamp Rats and Busse Combats, so while my question isn't about them or the steel they're made of, I'm going to ask for a bit of latitude. Specifically, I'm interested in O1 -- as a general rule, how "good" is it? I see that a lot of low-volume, "backyard" or part-time knife makers use O1.

I've read that it's a non-stain-resistant steel, is fairly easy to heat heat treat without special equipment, and is relatively forgiving about the heat treatment. The ease of heat treatment makes it somewhat popular, but I haven't found much about it's toughness/edge holding/impact resistance. I recall a PM where one of the members noted that he really liked O1 knives, but the discussion didn't evolve into why that was. Is it one of those steels that's better for small knives but doesn't scale well into the stresses that a large hard-use knife will endure, or a general, jack-of-all-trades steel, but that there's better for almost all niche applications? I haven't heard of any large manufacturer using it, so my guess is that there's better if you have money to invest in special equipment.

Anyway, I'm just curious and have considered writing to one of the makers who uses it, but I'd expect them to extoll O1's virtues and gloss over any shortcomings. So, this is an attempt to ask folks who may have insight, but without a vested interest in promoting or denigrating O1.