How would you use it in an IDE? For pair programming?

Certainly can't imagine it would replace source control - it would be incredibly frustrating having other devs break your codebase all the time, you'd be debugging all their mistakes as well as yours, and as a team we'd be disincentives from making any big changes since it would halt anyone else's work while the change is being worked on.

There's a reason we create abstractions like commits and branches, and don't all just work from a share drive.