They are useful ,i have 1 of those you listed and 2 larger ones just like it. All came from sams club for about $50.I think the lasko blower that I linked is rated around 350-375 CFM from what I can find.
I use them for drying carpet,ventilating areas for painting and blowing insulation. And of course now for distributing the heat from the wood stove up 3 floors.