Long-standing, time-wasting bugs I've noticed:
- Mdns broadcast disabling doesn't work.
- Swift playground in Xcode crashes regularly.
- Mobile Safari regularly crashes randomly on backspace in text areas.
- App Store installs corrupted apps but they don't show as corrupted until reboot, and then future downloads fail.
- Mail.app synchronously hangs the UI when processing new email notifications (probable not using a background queue).