I have always felt that in a self-defense situation that if anything more than very basic sights are needed, the threat is far enough away that it might not be considered self-defense.
There is a kind of truth in that, but probably the better way to say it is that the primary need in self-defense gun sights is high visibility, as opposed to a fine degree of precision.
Most instructors teach a continuum of sight picture development as you move from contact distance (no sight picture, firing from a "retention" position with the gun off the line of sight), to a couple of yards away (using the gun's profile superimposed on the bad guy you are focused on), out to the 7-15 yard range (where you're just getting the FRONT sight visible on the center of mass), and then beyond that (where you start to need to incorporate the rear sight and "dress" the sight picture for precision).
That last category, where you're needing to finely tune the sight picture is really low probability in defensive shooting. If you've got the time to do that, there's a good chance some other solution to the problem would be better.
Having a large, bright, high-visibility front sight then helps draw the eye and get the sight incorporated into your continuum of sight picture refinement sooner (i.e. closer distance) in the scale, which is a good thing.
The fine, precise, usually all black target sights a bullseye shooter needs to be able to precisely place shots on a 50 yd. bull are the opposite of what a defensive shooter needs to locate and place that front sight on a body mass in the 10th of a second s/he has to orient the gun before pressing the trigger.
The RMR style dots are very nice in competition and seem to be starting to prove their worth in the real world, too. There is some question of whether there is any benefit to them in that critical 0-5 yd. space where most defensive shootings happen but, with practice, it seems safe to say they probably won't slow you down. And for hitting those "occasional shots out to 35 yds" (per IDPA) or really long USPSA shots they are indeed awesome.