Thanks! That's definitely helpful feedback. That gets much trickier since both users essentially need to either share the R execution environment or have some snazzy way to intermittently write things to disk / read from disk / etc.
It's definitely a useful case to have in mind, though! I'll be sure to share it with the IDE devs!
One random thought if you want to poke at an implementation - you could try creating an RStudio Add-in that maps a shortcut to save your environment to a specially named (i.e. not *.RData that gets loaded on startup) file, or syncs to that file, or something. The diffs are going to be the hairy part, though... what do you do if both of us have defined a different version of an object? 