Softpoweroff locked the screen and keys regardless of whatever happened. It's broken, but they know how to fix it (see bug 2400), but won't share.

Anyhow, in the meantime I've found the most reliable method is:

- Disable auto network connections
- When you want to "lock" your device, first do Offline mode, then Lock Device.

This should keep most of the pop-ups from starting up your display. I agree, this is annoying and, I'll say it again: I WANT MY SOFTPOWEROFF back!

BTW - Be sure to check your screen status (on or off) when you plug or unplug something (headphone, power cable, I assume USB)... even in Offline mode/Lock Device this action will wake up your screen.