ukpokemonpro is right about the european/american boosters. I live in Belgium and I just bought my first packs of Ex:R&S this weekend. In my first pack I got hitmonchan ex, which was the only rare card in the pack. This was the last card in the pack. Because of the previous post I checked my booster packs and this was an American pack. It had the text 'For sale only in North America'. Now my friend Fleur also got an ex pokemon in one of her first booster packs and that pack was sorted like this: 4 common, 1 ex (which replaces the normal 1 common or holo), 2 uncommon, 1 foil (in this case it was a rare card), 1 rare. And I asked her about the package and it appeared to be a "For sale outside North America and Japan" pack, like ukpokemonpro said. So if you buy an American booster, the ex card replaces the normal rare card and is the last card in a pack. If you get a non-american booster the ex will replace one common card, like any regular holo does and you still get another rare.
Another thing irwinmalek mentions is bends on the cards. Well, I've experienced it too. Even though I put the cards back into the booster after I opened it and kept them there until I got home and put them in a sleeve and binder, the hitmonchan ex still had this little bend on the holo border. I can't explain why but the nintendo cards seem to be a lot easier to damage. At least that's the impression I have. I'm pretty sure they use the same type of paper as WotC to print their cards on. So this is a big question mark to me.