The migration itself was notoriously bad (check the forums from around that time, full of really confused people with unbootable systems), though it's likely usable now.
I was using fedora religiously (I mean, _really_) between Fedora 15-21, and systemd was actually what caused me to get off of the distro, the upgrade path was truly awful, even for Fedora.
The response was "but it's bleeding edge, what do you expect". And to be honest, I expected better.
Also it meant I had to unlearn a lot of my linux knowledge, and it was specific to fedora at the time.
Also, systemd in its early days was astonishingly broken, and many of the gripes you hear of today likely stem from people who were exposed during that period. (such as binary logs getting corrupted and unceremoniously truncated, boot being non-deterministic meaning your machine didn't boot 1 time out of every 10 and huge smatterings of "waiting for 1m 30s" even with very commonly used packages on a base system).
All that to say: I haven't seen a smooth transition from a non-systemd distro to a systemd enabled distro.
Although, truthfully, I haven't upgraded a Debian installation in-place.
I was using fedora religiously (I mean, _really_) between Fedora 15-21, and systemd was actually what caused me to get off of the distro, the upgrade path was truly awful, even for Fedora.
The response was "but it's bleeding edge, what do you expect". And to be honest, I expected better.
Also it meant I had to unlearn a lot of my linux knowledge, and it was specific to fedora at the time.
Also, systemd in its early days was astonishingly broken, and many of the gripes you hear of today likely stem from people who were exposed during that period. (such as binary logs getting corrupted and unceremoniously truncated, boot being non-deterministic meaning your machine didn't boot 1 time out of every 10 and huge smatterings of "waiting for 1m 30s" even with very commonly used packages on a base system).
All that to say: I haven't seen a smooth transition from a non-systemd distro to a systemd enabled distro.
Although, truthfully, I haven't upgraded a Debian installation in-place.