There bad side is, if you get to close to their nest or disturb their nest, they will attack without mercy
unlike honey bees they don't lose there stinger when they sting you and can do it over and over :'(. You can mow over them once in the hay field, but the second and third round is a different story.
They had a nest under my uncles brush cutter, and when he went to hook it to the tractor ( not knowing they were there) he took over 260 stings. Never had one sting me when they are working flowers, but have got to close to there nest and paid for it.
They will sometimes warn you if your getting to close to there nest by flying in front of you and zig zaging back and forth, just back up slowly and they won't attack. That's what i've learn from them, the hard way.
Jack