A while ago I had been working on a native Mac slack app. I was 70% complete but sidelined it. Should I pick it up again? Would ppl here be interested in paying for something like that? Here are some links to screenshots so you know its not just vaporware :)
I believe it would get a fair amount of attention if it were open sourced. There's lots of Apple platform devs out there who'd love to have a more native Slack experience and would contribute to such a project in a heartbeat (myself included).
Most users will accept issues with their free program if the alternative is to pay. I'm pretty sure the message pane you have there is a WebKit controller so it is debatable how native this would be.