I have a Ruger PC4 (40SW), and I love it, its one of my HD guns. I live in a neighborhood where the houses are basically about 15' apart, so in defending my home, I would want to minimize over-penetration of walls, so I think its better suited than a rifle caliber. If you run out of ammo (or I suppose if it jams, but its never done that), its very solid and fairly heavy, so it would make a great club!
Several people have mentioned that pistol caliber carbines aren't any good out to 100 yards... that's not surprising, but I don't think that makes them useless. In HD situations, for instance, my whole property isn't even 50 yards long. I did actually scope it at one point, and depending on the ammo the bullet drop at 100 yards was 5"-8" (IIRC), and the groups (for me) were right around 4", just as a side note.
I also have a Marlin 1894C (.357m), and while the round has a lot more punch and useful range, I don't personally find a lever action to be a good HD gun. I want to be able to load it quickly in the dark, and unload it easily before I store it -- nothing like magazines for that.