-that it better matches the spoken cadence of sentences;
-that it sometimes reduces ambiguity; and
-that its use matches practice with other means of separating items in a list (example: when semicolons are used to separate items, a semicolon is consistently included before the last item, even when and or or is present).

-that it is against much conventional practice;
-that it may introduce ambiguity; and
-that it is redundant, since the and or the or serves by itself to mark the logical separation between the final two items.

Do you use the serial comma? I, for one, tend to avoid it, since it's against the punctuation principles I grew up with (the Romanian and French ones), but lately, my teacher of Technical Writing recommends that I stop avoiding it...
His main pros are mostly what Wikipedia says:

My counterarguments can also be found in the Wikipedia article:

I'd really love to hear other opinions.

In a series of three or more terms with a single conjunction, use a comma after each term except the last.
Thus write,
red, white, and blue gold, silver, or copper
He opened the letter, read it, and made a note of its contents.