Over all my barn is great. The BO/trainer is a complete control freak, but it means everything is run well.
The biggest problem I had was another boarder feeding my horse. She was the one I bought him from, and I guess she feels she knows him better than I do (even though she's never ridden him, bought him from an auction, and only had him two months!) She started feeding him this really sugary mash stuff she was giving her old, retired horse while I was on vacation. Painter wouldn't even eat his own food for a week (wich meant he didn't get his much needed meds)! Worse still, Painter is on a special, high protein low carb diet. He isn't even supposed to have apples, let alone high sugar mashes

My BO caught her doing this and basically told her if she EVER messed with any horse but her own again she would be kicked out of the barn