What we ultimately lose with systemd is modularity. If we cannot upgrade systemd without also upgrading the kernel, then systemd might as well be considered part of the kernel.
I think there was already at least one visible problem with systemd stepping on kernel developer's toes (so to speak) by re-using one of the debug flags.
Heck kernel is monolithic. But thinkign about it, I trust kernel developers a bit more than systemd guys. Maybe it is just a new project and it will stabilize at some point in the future. Now they are kind of shooting from the hip (adding ntp, udev, network socket pools, logging, ... ). That tells me "hello lockups and freezes" and being back in the mid 90s on Windows restarting every day.
Gentoo's eudev is more relevant now than it ever has been before.
http://lists.freedesktop.org/archives/systemd-devel/2014-May... (via http://redd.it/2a2tz5):
> Also note that at that point we intend to move udev onto kdbus as transport, and get rid of the userspace-to-userspace netlink-based tranport udev used so far. Unless the systemd-haters prepare another kdbus userspace until then this will effectively also mean that we will not support non-systemd systems with udev anymore starting at that point. Gentoo folks, this is your wakeup call.