I never really got up to speed with radio nav before my test. Not really a problem, the old school method sufficed, BUT - if I did it again, I would have learned my Radio Nav properly - it's such a reassurance.. .. .MS Flight sim is a nice fun way of learning your VORs, and how to think them through in flight, without all the pressure of a real plane to fly. (For something more 'official', there's also RANT).