ResetAll resets all of the rows. It is just as good. Technically slightly less efficient. It only applies to calculations. Things like Total are recaculated when requested, so it wouldn't effect that.
Unique marked columns are to identify a unique row in your cart. The t-shirt example you gave is a good one. If you had two t-shirts, one red and one green, then the id alone wouldn't be enough to identify a unique row in the cart. You have two rows with same id only with different colors. In this example you would then have to pass both the id and the color to get an accurate index.
I did mean the eCart object item array. I was just imagining a dynamic site populated from a database that might drive that content.
Did this help? Tips are appreciated...
