If you stack your apps by categories or by your usage patterns,
the stacks become like different screens with pre-open apps.
Great feature for multitasking!
It is a brilliant idea. Stack is basically a window multiplexer, reminds me of tmux in terminal. I also understand team's focus on Mac, window multiplexing on Mac is not really that great (limited to 2 panes, only vertical no horizontal splits possible), though I've heard great things about Windows implementation - so while windows adoption can be slow because of great OS offering, on Mac it has quite a potential.
Seems very useful app for Social media workers. Good Job!