sharke
[...] It's not a glamorous feature to tout [...]
I disagree with this, since I feel this is the foundation required for elegant arrangement. Being able to chop and drag "chunks" all over a project without concerns for markers/automation/takes/etc. would make sandboxing go at lightning speed and not distract the user from composition. If it is a "completely vertical" section, markers, tempos, and automations should all go with it, and snap to sections they but up against. From the same reasoning, being able to hit Ctrl-A and drag that vertical section would allow the entire project to be slid left/right (or even grab the timeline and just move it - keeping all else "relative"). As alluded to, most video software has these features baked in (ripple delete, clip snapping, etc.) solely because people hate to watch "black screens" during a video.
As Craig mentioned, I too sandbox audio (even for what will eventually become MIDI parts) only because I can drag/drop those all over without little worry. When a "what just happened" snags me, I am often done for the night.