Help with Sony 777 SACD

I have a Sony 777 and am wondering what the switch on the back of the unit that allows the user to unscrew a plate on the back and swich from standard to a custom setting. Is this a benefit to the sound quality and is there any danger of harming your system?
The consensus says it sounds better on custom. I have tried both and can not notice any difference but, keep it on custom anyway. "Standard" is supposed to roll off the very high frequencies, "Custom" does not. No reports of any damage have been experienced by anyone using custom.
I find "custom" lets too much garbage into your system, makes the sound less firmed-up. Highs are better, but bass is thinner. I'd try it both ways, no harm is likely, but I think the standard position is best in most systems.
The Custom setting is better in my system. Better space/dimensionality, microdetail and imaging.
I disagree with Estmad's genralization. The results would be system/preference dependent. In my system, with the SCD-1 used in the "Custom" mode I noticed a slight improvement in the "openness" of the sound stage, coupled with slightly better extension in the treble without any loss in bass extension. In fact, the bass seemed slightly more focused and defined in the Custom mode. In summary, there is an overall improvement in the sound of the system, albeit, more subtle than "earth shattering."
I would agree entirely with GMorris. Switching to Custom opens the sound up more on SACD on the SCD-1 (I listen to CD though an external processor). If you were auditioning a new component for an upgrade, you wouldn't pay a great deal for the change, but for the effort of moving a screw and flipping a switch, it's certainly worth a careful listen.