I think the biggest myth with the shotgun is indeed the "don't need to aim" one - followed closely by the "can't control recoil" and "too big/long to use indoors" ones.
Towards each:
Patterning the gun is definitely something that needs to be done, for any serious-use shotgun. And to those who suggest that the shotgun can't "be surgical?".....
From Active Self Protection - shotgun
As a shotgun owner and as one who has it in his defensive arsenal, I know how mine patterns, and at what kind of distances I can take what kind of shots, with the specific ammo that I've loaded the gun with (note that some shotgunners will go so far as to re-pattern the gun if they simply switch ammo
lots). As someone who lives in a dense, suburban area, I have to keep the backdrop in-mind, always.
I also believe that those looking to use a shotgun for defensive purposes really need to understand how to best cope with the recoil of this extremely effective defensive weapon, as well as how to better manipulate it indoors. For both of these, Rob Haught has some very good and very readily learnable techniques: the "push-pull" and "short stocking."
The last two concerns are rather easily rolled into one, I think: the need to run the gun's action (if manually loaded) with-authority (and as soon as the weapon has been discharged), and the need to realize that the shotgun tends to be a rather low-capacity weapon, and basic ammo management should be ingrained into the defensive shooter's base weapon-manipulations skills ("if you're not shooting, should be loading").