I have the Cold Steel Safekeeper I, the 6" model, which by the way I don't seem to see for sale anymore.
bought it for fun, really, because I use a CRKT folder on a daily basis, but I did carry it for a while. I found it somewhat awkward to use for the mundane tasks I had for it (box cutting, letter opening, wrapper peeling, bottle wrapper taking-off, etc) but fun to use in poking at things. so that's it, really, for me: it was a sh*ts & giggles type of splurge to pick up. nothing wrong with that in that particular context.
more to the point, for what job do you have in mind for this particular tool? have you considered the repercussions of using it in a not-so-clearly defined self-defense scenario, if that's your anticipated application? it's GALLING to have to consider being second guessed in this fashion, I know, but you have to consider how it's going to look to a DA when s/he looks over the facts of a case, pending possible prosecution. personally, I'd prefer it if a tool I carried had more than one use, for more than one job. there's a saying in backpacking, "If something you carry does only one thing, it's not pulling its weight." FWIW and all that.
I read somewhere (possibly in the Cold Steel lit) that push daggers were favored weapons during the Gold Rush, but I might point out that the times back then were not nearly so litigious.
in a purely academic sense I've trained with knives, but it's way far down the list of things I'll want to use in a self defense situation.