Here is an interesting article about Pat Venditte, a pitcher for
Creighton, that is a switch pitcher. There are a lot of benefits,
obviously for better match ups, differing delivery styles from each
arm, and also an increase in durability because he alternates throwing
arms.

The rules regarding a switch pitcher are also interesting:

QUOTE:

"Umpires working Creighton's games have to dust off seldom-used rules
regarding switch-pitchers. Like everyone else, Venditte gets only
eight warmup pitches upon entering a game and five before any inning,
whether he chooses to throw left-handed or right-handed, and may not
warm up again if he changes arms mid inning.

A switch-pitcher facing a switch-hitter could make a fine Abbott and
Costello routine. Against Nebraska in 2006, a switch-hitter came to
the plate right-handed, prompting Venditte to switch to his right arm,
which caused the batter to move to the left-hand batter's box, with
Venditte switching his arm again. Umpires ultimately restored order,
applying the rule (the same as that in the majors) that a pitcher must
declare which arm he will use before throwing his first pitch and
cannot change before the at-bat ends."

LINK:

http://www.sptimes.com/2007/04/08/Sports/The_kid_s_all_right_a.shtml