- Startup time feels subpar - I haven't dug into it, but it feels like it's downloading the JS for the app on load every time. Switching between teams is similarly slow on first access.
- Scrolling up to something that happened fairly far back in history can feel really awkward and broken, image loads and ajax fetches can make the scrollbar behaviour really janky (to be fair, I just tried this and it was better than I remember, although still far from perfect)
- Switching rooms takes about a second, even if I was just in that room, which while not horrible, is still a little laggy for something that should be nearly instant if I have the room's content cached.
Overall while it's gotten better, the "native" Slack app still feels very much like a webpage with OS chrome around it (which is what it is, but other apps like VS Code, Atom, and Discord don't give this impression nearly as much)
This is all on the latest Macbook Pro upgraded as much as possible in every respect save the video card.