Quick Selection Tool - in-depth questions

Hello, some detailed questions about the new Quick Selection Tool in CS3:

1) What can be achieved by changing the "hardness" (sorry, no English version) in the brush options? In his video, Russell Brown recommends to have the "hardness" on 100 percent always - why? What's the difference if i reduce the "hardness"? I couldn't really find out.

2) Does the tool "remember" wanted/unwanted colors? Brown recommends making a first selection, then Alt-dragging the tool around unwanted areas - thus the tool would "remember" unwanted colors. I tested this intensely, but cannot really prove his statement.

Any in-depth experience would be great! Thanks!

1) You have better control over the selection, if your hardness is at 100% (you see what you are painting over, in contrary to a soft brush).

2) Yes, the tool remembers your choices for the TOOL SESSION.

3) Yes, changing out of the Quick Selection Tool erases the memory for the tool session.

Thanks, Mathias, for clear answers!