I'd say don't listen to your mate. Owned a couple, and seen a few more, and all were very good dogs. Some people slate them for having poor feet, but to be honest, I've not seen one with bad feet. They aint going to have a coat like a collie cross, but it doesn't stop em getting into cover when in persuit, and they're as keen, or keener than other types, to run anything.
Maybe a slightly smaller type might be better for just ferreting, but I did alot of lamping years ago with mine, and found them very versatile ?