I know it's a bit odd, but I like using my TI-89 graphing calculator in addition to an E6B when doing calculations. It helps me avoid dumb arithmetic errors.
I read the section "Use of Test Aids and Materials" of Recreational Pilot and Private Pilot Knowledge Test Guide (FAA-G_8082-17). It seems to meet all of the requirements except (d), which I don't really understand:
The use of magnetic cards, magnetic tapes, modules, computer chips, or any other device upon which pre-written programs or information related to the test can be stored and retrieved is prohibited.
Does anyone have a definitive answer on whether these types of calculators are permitted?