My boyfriend's in the Army Reserves, currently in the process of going full time.
But no, strangely I don't know anyone doing the GAP year. As I'm guessing the point of the year is to recruit people long term, I'm guessing you'll get to experience some of the snazzier aspect of the military... just be prepared for the not so snazzy aspects.
Discipline, exact schedules and procedure, deliberate locational inconvience, fitness assessment, tough conditions, emotional stress (relationships, etc), subtle conditioning... but that's all pretty common sense stuff to consider I spose.
Depending on who you are, it can be worth it. Just make sure you really want the military lifestyle - because their intention is to get you to sign up.
Sorry for the useless post
=> Jess