I'm running a dev preview of macOS Sierra and noticing some mouse lag on my attached screen. I realize this is a preview and not fully supported yet, but is this a known issue?

That sounds like pretty good news Carlo Have you heard if those fixes are being backported to 10.11.6 too, or will we just have to forge ahead with Sierra if we want those?

Same issues here as everyone else. Lag, lockups, etc. Dev preview 3 16A254g MacBook Pro (Retina, 15-inch, Mid 2014) There is a delay waking from sleep as well. If you need any logs or things like that, I can send them