I did match in cards.
I don't have any great advice except to try to keep it to 1 page, and do not do something stupid like use bad grammar, bad spelling, or say something outlandish. Also, if you have a strong interest in a particular hospital, I would add something/a paragraph to your basic PS mentioning why you like that hospital (i.e. My interest in Duke cardiology stems from its history of clinical and research excellence, particularly in the areas of X and Y [pick subspecialty of cardiology that you have an interest in and that this medical center is well known for]). Just one idea.
I'm not sure the PS really is that important, at least until the stage of interviews. "Numbers", where you did residency and your letters of recommendation are most of what gets you in the door.