Gates of Fire would've been a better movie, as the book is well written and historically more accurate. Either way, it's a story worth telling.
BTW, warfare has NOT changed much. Many tactics used today were invented and perfected by the Greeks and Romans, and I'd venture that they were more proficient as warriors than soldiers today. Spartans trained for 12-13 years to be soldiers, before ever fighting a battle, as opposed to mere months of training here. They understood the psychology of war, and applied it, better than modern militaries. Take away our toys, and they'd have it all over most modern soldiers, I'd bet.
Molon Labe!