I really liked this. I especially thought this was hysterical:
"Your blue brooms will become an icon of greatness among Quidditch followers the world over, uprooting conventional broomstick wisdoms and long-held broomstick myths, inspiring poetry, song, perhaps occasional performance art—"
mostly because I'd like to see performance art on brooms.
I liked your Snape and Harry, and I didn'tmind the infidelity one bit. It was a great take on the prompt. Woot! Go you!