As for development/hackability: you need to understand ostree, rpm-ostree, and flatpak fundamentals, not be afraid to layer packages where containerization is impossible or inconvenient, and accept that cookie-cutter configuration recipes intended for other distros aren't likely to work.
I'd also recommend distrobox over the bundled toolbox for managing distro environment containers, because useful additional features.
With all that said, I've been using Silverblue+Kinoite daily as a development (Linux + Windows in libvirt-managed VM) system for over a year without no regrets whatsoever, and only trivial complications (e.g., running a trivial shell script to rewrite JetBrains Toolbox-created .desktop files so JetBrains IDEs run in my preferred distrobox container when launched via GUI).
As a shout-out to another Fedora immutable distro, I've also switched to Fedora CoreOS for new home office network service deployments and this has been similarly pleasant and hassle-free.
Can you give some examples? I've been using Universal Blue's silverblue-nvidia extremely happily for a couple months now, and haven't had any issues with it. It's been a great and extremely smooth experience