Are M1 Macbooks good for container-based software development (Docker...) in Q4/2021?

I say yes indeed. I'm all in on the future direction Apple has staked for Apple Silicon and use M1 / iPad for everything I can and will set up a linux VM or pay for cloud VM as needed when I have to have code that just isn't possible without Intel or kernel extensions for OS prior to Big Sur. I haven’t installed Rosetta 2 on my daily driver yet as well.

• Docker was GA for Apple Silicon April 15, 2021 and now doesn’t require Rosetta - https://docs.docker.com/desktop/mac/release-notes/
• VMware is still in preview, but October update should drop soon - https://blogs.vmware.com/teamfusion/2021/09/fusion-for-m1-public-tech-preview-now-available.html
• VS Code and rosetta / homebrew have been awesome for me in testing and peers using it in production (especially since they work so well with cloud in Azure and work pays for that service) - https://devblogs.microsoft.com/visualstudio/developing-on-a-m1-mac-with-visual-studio-for-mac/

You can certainly find some pain points if you go looking at software revolving around kernel extensions or not updated in the last 24 months for general OS changes. Hopefully you can refine any big show stoppers for your critical projects and buy with confidence after some research and other people share their experience. I personally find instant on and the battery life and performance of the initial Air so good, I can't imagine I'll ever get an intel again other than maybe next year's bump on a Mac Pro if I decide to retire my 2013 Mac Pro home lab which takes much of my legacy code lifting off my portable.