Eh, this is a bit hyperbolic in its headline, but it's certainly been an ongoing discussion within the community for some time (the latest ATP episode revisited the topic).
It's not "hate" as much as things have gotten sloppy. There are always irritants in any software, and Apple's isn't immune from that whatsoever. Mostly it comes down to: 1) pre-existing or new bugs (e.g., the Preview bug listed in the article), 2) their inability to consistently get software services to work (Apple Music) , and 3) over simplifying the design of applications to bury or kill commonly used functionality (the new Photos). iTunes and Music are along the same lines, but in the opposite direction: Way too complex on the UI, and the that a lot to do with the kitchen sink approach that iTunes/Music take.
The biggest bugbear of late has simply been Apple's inability to get their act together with services, as more and more software leverages services, and Apple just can never seem to quite get it to be rock solid. Gruber noted as much with regards to Photos, and Siracusa has with contacts, but it's a pretty common problem across their product line.
And I'm sure plenty of people have been endlessly prompted to re-enter their iCloud password, without context, to authorize who knows what.
That said, most of the apps work fine 80% of the time, and they generally work pretty well. I am amused at someone suggesting using Evernote over Apple's internal app equivalent, since Evernote has really gone on a downhill slide in performance and quality of late. PIMs always seem to start strong and then quietly whimper off into the night (here's to you, Yojimbo). Notes, Reminders, iCloud Drive, and Mail have all been rock solid for me, although I'm not a big Mail user altogether.
And Windows 10 is great, but that's relative to Windows 8. It still has its issues, and those issues (unfortunately) tend to be much bigger things like being unable to upgrade to Windows 10, even though everything should work per hardware requirements, licensing, etc.