If you're genuinely interested in some discussion pertaining to the answer to that question, use your favorite search engine to search HN for likely phrases and skim until you find some discussion with a significant volume of commentary.
Because of its political nature, this is a topic that's best not discussed unless you have some very specific questions or observations, and you are already very well informed about the merits and faults of both the systemd project and most of the other pieces of software that provide similar functionality. :)
There's basically three non-reasons to hate systemd which crop up the most:
1. Its lead author is a bit of an asshole, plus lingering resentment from Pulseaudio.
2. Systemd is not sysvinit, so some of the system administration people learned doesn't translate.
3. Systemd contains functionality that people don't think it should have (usually presented without any argumentation as to why it shouldn't incorporate those features, so it tends to come across as akin to saying that Firefox is bad because web browsers shouldn't have video players built in).
The main reason that does come up that's not really a non-reason (but, I should note, is hard for me to validate as a dispassionate neutral observer) is a fear that systemd is being rammed down users' throats against their wills, partly by distros deciding "there's no alternative" and partly by systemd incorporating ever more tools.
It also is people holding onto the 1970s Unix system architecture and philosophy. Linux is Unix like and systemd is just a better modern system, but others philosophy on systems just won't allow them to support it.
I would not mind systemd, except that logind depends on systemd-init, and DEs are increasingly dependent on logind for various reasons.
For example, more recent versions of upower are just a wrapper around logind. Thus to have a laptop sleep when you close the lib, you need to replace your init process.
It has a common point with systemd : the lead is Lennart Poettering.
Sound on linux is a mess. And pulse audio is vastly blamed for it. Complex circonvoluted architecture that overpromised and under delivered..
The guy loves to brag about how he is the messiah of a problem and will fixt it, make galaxy like software that are unstable and leave a mess after his doing saying my job is done, let's work on another project where my genius is needed.
But, after utterly messing up once, notably at the (lack of) design level, he has been entrusted to no overpromise again and make the ultimate revolution for the init process. A lot of coders did not believe in his repentance for the mess in pulse audio : he may be as arrogant as linus torvalds he is as smart and a good coder as rasmus lerdorf.
The PID1 on linux is now known as a solar system of processes with nice chaotic trajectories and astronomers are seriously planning to use systemd alone as a nth body interaction simulator.. unexpected .
I switched from desktop Linux to Windows entirely because of Lennart Poettering. Audio was a complete disaster, as you mentioned. (This was only a few months ago.)
PulseAudio seems to get by far the most development and support. I tried ALSA and couldn't get any sound at all, and it didn't seem to be very well integrated into my shell. I did get ALSA to work on my laptop, but there were still lots of tradeoffs.
Because of its political nature, this is a topic that's best not discussed unless you have some very specific questions or observations, and you are already very well informed about the merits and faults of both the systemd project and most of the other pieces of software that provide similar functionality. :)