I loved Mercury when I saw it originally. I didn't know about makespace but that looks great too.
The main thing that struck me about Mercury isn't just the clean UI but that the software is organized around 'app-free intentions aka flows'. All operating systems (iOS, Linux, Windows) are very app oriented. Mercury provides your 'intention' or 'workflow' as a concrete organizational model. Typically you jump from app to app to app to acomplish a given intention - the thread of intention just lives in your head, but nothing connects the corresponding windows on your screen. Mercury solves this.
Check out this 'flow' of a single intention (getting coffee with a friend) that spans multiple apps - nothing like this exists in any mainstream OS:
https://miro.medium.com/max/1000/1*0hAZt7GMWzgSjSDK5VBwCA.gif▾
I would
love to create threads that connect snippets of information across multiple 'apps' - all are related to one intention. Unfortunately what I do is just reframe a calendar view or mail view I already have open (for one purpose) to another purpose. I end up with a cluster of app windows with different purposes all mixed together. Not at all ideal, but something we're just used to I guess.