Drilled, (and slotted to some extent) rotors are mainly cosmetic for street use and can even introduce unwanted problems such as heat/stress cracking that plain flat rotors would not have. Especially if quality of castings is poor.
Track cars use them frequently, but that is with the understanding that they are changed out after very little use.
With that being said, I personally like the look of drilled/slotted rotors & don't mind installing them as long as they are quality units. Actually, rotors that have the holes cast into them vs. drilled afterwards are better & hole chamfering is a must. Dimpled rotors don't have this problem as they are not thru hole and there are no edges for cracks to propagate from.
I have upgraded Baer GT+ system on my T/A with cast in holes/slotted 2-pc rotors that are much bigger than stock, 6 piston front calipers/4 piston rears, Hawk pads, & the braking performance is phenomenal! With that system there was no flat/blank rotor option.
I do plan on getting a set of the ECSTuning drilled/slotted rotors to test out in the near future - but again, in the case of my DD BMW, this is simply for looks and the rust free coating
Their pricing is very reasonable - just hope that doesn't mean degraded quality...