I reproduce artwork, and the scans I work on are often several gigabytes. I fell in love with the idea of having a "master" scan document that included touchup work, then having "derivative" files linking to the master one for each printable version. (One "derivative" file for each paper or canvas type having its own soft proofing adjustments.)
I'd love to be able to have the master document open at the same time as a derivative file, on separate monitors, and see the derivative file update in realtime as I make changes to the master document. (By realtime, I mean once I let go of something like clone stamp, without needing to save.)
That's what I thought I was getting. Doesn't seem to be the case.
Also have my fingers crossed they'll make an option to not copy as much data into the derivative file, and truly rely on being able to find the linked file. 1.87GB "master" PSB file. Derivative file is the same dimensions, merely has the master placed as a linked smart object without so much as an adjustment layer. The derivative PSB file is 1.62GB. ("Maximize PSD and PSB File Compatibility" is "Never", so that's not forcing a flat save of the document.)