Explosives, dude. 
I’ll pragmatically go for the “open here”, most of the time - except when I forget to look, and then get roundly ridiculed by someone who sees it 5 minutes after I started tearing at the thing :).
I usually ‘open here’, especially if it’s something I’ll need to close again, since it’s usually easiest to close (or, at least attempt to close) the package again and not have a giant mess on your hands if you do so.
Another grrr for hard plastic packaging here. Forget the scissors, pass me some gardening shears.
I open right where they advise me to. If they’ve spent enough time to research and design the best possible way of opening something, I may as well use it.
Except for cereal. Like **TheLoadedDog **I always have trouble, and I’ve been opening cereal boxes since I was a kid! Now I take the bag out completely, throw away the box, and use a chip clip on the bag.