1) Rarely breaks. Worst I've seen is needing a permissions tweak after an OS upgrade, in many years of use. Back when I switched from Macports I switched because ordinary usage kept rendering Macports so goddamn broken that it was easier to nuke its directory and start over rather than figure out how to fix whatever my bold command of "install package" had destroyed this time. I've never seen normal or even slightly abnormal use put Homebrew in a broken state that required manual intervention to fix.
2) Command line UI is alright. This should be a given but isn't always.
3) Can manage proprietary software for me. There's almost nothing I use (maybe actually nothing?) on my Mac that Homebrew doesn't have an up-to-date package for, aside from Apple-provided apps.
4) Enough people use it that despite being a semi-free-for-all community-run thing packages are pretty much never broken, including the proprietary ones. I'm also continually surprised by how often I find some obscure thing with five stars on Github, want to try it out, and sure enough, there's a Homebrew package.
5) Lets you manage your packages with ordinary user-level permissions. No root elevation required.
6) I can clean practically all of what it's done and get back to a nearly-vanilla system (with the exception of some of the proprietary apps) by deleting one directory. My system and GUI will still boot like nothing's happened. IMO keeping your user-level packages strictly separate from the system-level ones, and managed totally separately, is absolutely the right way to go. I didn't realize how much I wanted this until I started using Homebrew on a Mac, after many many years of Linux package management.
7) It leaves system-level packages that it upgrades alone, so doesn't break core system stuff (I would fucking love this to become a norm on Linux—system uses and assumes latest LTS version for stuff like Python, but I can install whatever version I like for my own use, without affecting that whatsoever and without having to use a different goddamn version-management tool for every single language)
8) I'm pretty sure you can have more than one version of something installed at once and there's a command to switch between them (juggling symlinks, probably), but my recollection of this is vague and may be wrong.
9) If you're actually doing multi-user on your desktop/laptop I think it lets you have per-user install directories and active packages—but I don't really know anyone who does this, and haven't known people to share a computer, really, since over 15 years ago. Amusingly enough, iPads, with practically nothing resembling multi-user support, are the exception to this use pattern, as those seem to get shared among members of a family all the time.
Bad things:
1) Requires Ruby (seems like a dumb complaint, I know, but I hate installing an entire scripting language for a single command line tool, and no not all Linux distros ship with Ruby by default, far from it)
2) I dunno if it still does (I'm working mostly on Debian now) but for approximately forever it's had a completely braindead default for how often it auto-updates its package list when running other commands, and you had to go change that every time you installed it on a new machine so you'd not rip your hair out in frustration when your command to install a package was delayed because it'd been a whopping 16 minutes since the last time it checked for updated packages. Why the hell this didn't default to, like, 12 hours or something is entirely beyond me. AFAIK everyone hates the default behavior, to the point that it's become a common jokey-reference among Mac nerds, and I've never been able to figure out why anyone would want it.