Superhuman user and former Grammarly user here.
I'm a big fan of Superhuman as an email client and happily pay the premium price for it. I really hope they don't change what makes it great.
I used to love Grammarly until they essentially ruined their product - much like Dropbox did. They took an app that worked perfectly and deprecated it, replacing it with an invasive keyboard replacement that was supposed to work everywhere but performed poorly across most programs and included functionality I wasn’t interested in that is kept nagging me to use. When I complained about the issues, instead of addressing my concerns, they sent form letter responses about their commitment to privacy rather than fixing their intrusive software.
This reminds me exactly of Dropbox's transformation from simple, reliable file storage into bloated software that cluttered my computer with pop-ups and background processes. When users complained, their team never seemed to understand why we were frustrated. Then they started acquiring other services I eventually cancelled as they tried to integrate them into their core service. I eventually moved to iCloud and never looked back.
I hope Superhuman keeps their current excellent email client that I gladly pay for, rather than replacing it with some "next generation" product that nobody asked for and that would likely be inferior to what we have now. I genuinely love Superhuman as it is.