Hate to beat a dead horse, sorry for the pun. I think the magnetic stirrups are fine, like others have said they will not prevent you from falling off or messing up. They're an aid, and a prevenative measure, not going to put you in the winner's circle. They're FEI approved as well, just an FYI for everyone. I think jumping 5' 9" or even lower at that, riders have already achieved a lot, worked their butts off, and gotten to that point on their own.
Things that grind MY gears. Some rantish and geared towards certain people, others just in general.
-PHONES. Stay off it, I hate riding in the arena while listening to someone loudly gossip while they're on their misbehaving horse in the middle of the arena. Not to mention if it goes off and said horse spooks. Mine is set on the edge of the arena on vibrate or silent. Just a common courtesy for all. Then when you drop it in the arena sand, don't notice and my horse steps on it, sorry, not sorry.
-NOT CLEANING UP, as mentioned by a few others have the decency to clean up after yourself. You pick up your scraps from cutting hair, picking feet, old bandages and so on. Put your stuff away and don't complain when it's put back on your saddle washed and folded because the BO knocked it in the mud.
-DRAMA, the barn is my escape. I love horses, I love the barn, the poop, the dirt, the smell, everything. Don't ruin it please. We all go to the barn to enjoy ourselves, not enjoy you dish on an amazing trainer who loaded your horse in the trailer because she refused to get in after a trail ride. The trainer knew what she was doing and eventually your horse walked right in, she wasn't mean, she wasn't nasty. She's was completly correct, and that lesson should have cost you a lot of $$$$, she did it for free.
-THIEVES, ugh where to begin. You're covered in glitter, literally all the time, people at the barn do not appreciate you using their stuff, not putting stirrups back. We know it was you, glitter everywhere. If it's not yours and you use it that's technically stealing.
-KNOW-IT-ALLS- plain and simple. No one in the horse world knows everything. There are variations in training, different methods, everyone can have a different opinion. If you say you know it all, you're wrong, sorry. We're always learning as horse people, I always am learning new things either from this forum, experience and so on.
-THOSE PEOPLE, we all know "those" people. The ones who knock your riding, knock your friend's riding, your horse, your tack and so on. Mind your own buisiness and control your beast of a horse. While you were busy yelling at me, I watched your horse give you literally three warnings before she exploded. I warned you, and you cut me off each time giving an excuse till you were brushing off dirt and all that fancy tack was ruined. That expensive horse, is now wide-eyed and loose outside, would you care to knock my inexpensive, yet well-trained horse again? OR the people who think horses have feelings like humans, again sorry to pop your bubble they don't..
-TRAINING "AIDS" I'm sure we all know about these, tie downs, draw reins, a very strong, or punishing bit to cover issues, chains, pads and so forth. If used correctly and for an actual reason fine. I don't want to see it just because it looks cool or covers up holes in training...
Too many more to list. I choose to ignore most of it, but do have those few things that really grind my gears.
TL;DR - phones, not cleaning up, drama, know-it-alls, thieves, those people, training "aids."
"Every person you will meet will have at least one great quality. Duplicate it and leave the rest." --Clinton Anderson