The only real fault I could give it is that in my experience, if you're so tightly wired into external things that you become an essential part of them, that's probably not the optimal system design.
That really isn't the case with systemd; it basically depends on glibc and util-linux for "mount" etc. just like most other init-systems, but everything else is optional.
That upstream projects actually make use of systemd features like systemd-logind can hardly be a problem either; all the non-systemd platforms are free to provide their own similar services that upstream projects can use, so there are no problems there either.
I DO have a lot against the binary logging for very good reasons. I've worked with a lot of products that did their logging in proprietary binary formats over the years, and even when the internal data formats are well-published, the mere fact that intermediary services are required to access and format them has made their respective products harder to work with.
Some facts first; systemd's journal isn't proprietary. It is a well documented standard with a stable API and language bindings:
There are several independent journal readers already. I can't think of any non-contrived user case where it is a problem that the logs are binary.
In fact, I can't think of any non-contrived user case where old style flat text file logging is better than systemd's journal; it scales better in every direction and allows for powerful filtering in a much better way than using humongous regex lines, is much more secure, allows for a single collated system log and much better debugging, etc. etc.
Not forgetting that it is now possible to have reliable, robust logwatch scripts and even make a log viewing GUI that isn't just a glorifed "less" with windows decorations.
Just like you I have been bitten by (proprietary) binary log files (and much worse; binary config files). And just like you I was really, really skeptical about systemd's binary log format. But the more I used it, and the more documentation I read, the more I became really glad about it: systemd's journal just solves so many problems I have had over the years with syslog files. It is a really well thought out and well designed logging system.