I see they've updated the rules a bit. Back In The Day™, the rule was students were allowed "one handheld, non-printing calculator". Now, the rule reads:
Each student is allowed to use any number of calculators that are self-contained and battery operated; however, each student may use at most one desk. No computers are allowed in the competitions. Removable or interchangeable parts are permitted. Electrical outlets in the room may not be used.I guess you can't bring an HP Libretto or an Oqo running Mathematica.
IMSA still blows. :P