Add an "Are you sure?" confirmation to the cancel build button
I once accidentally clicked the Cancel button while a build was happening , and it had some pretty negative side effects since I did it in the middle of our deploy to production - whoops!
It was a complete mistake, and I think builds are cancelled with enough infrequency that adding a confirmation wouldn't be too awful.
Worst case, allow us to turn on/off the cancel confirmation alert on a per-user basis. I know I'd turn it on for myself, and I'd like to set it as the default for everyone on my team, too.