I also wonder how common these problems are. I live in San Diego and everything looks pretty-good to me. It renders my house in 3D and the turn-by-turn navigation worked great. There are obviously problems in some places, but so-far-so-good here.
In Switzerland, the information density is much lower in comparison to Google Maps and much of the still available information is wrong or out-dated. Outside rural areas, Apple Maps mostly shows a vast emptiness instead of mountain peaks, hiking trails etc.
There's definitely room for a lot of improvement …
After communication, maps are the second most important application on a smartphone for a lot of people. If those maps go from being reliable to being wildly wrong -- which, it seems apparent, has been the experience of a number of people -- then you can hardly expect them to not be upset.
If there were some perfectly reasonable explanation for why upgrading to the new version of iOS/Android/whatever caused text messaging to stop working reliably for a significant percentage of people, I expect we would see more or less the same reaction.
Of course, the fact that it sometimes generates utterly ridiculous visuals is no doubt helping the spread of the meme, but the underlying complaint here seems perfectly valid.
The bits that have been 'wildly wrong' so far seems to be the business integration (which is probably also the most easily corrected). I wonder if the people who went to the effort of posting screenshots with "lolz, this business should be here" actually reported where the location should have been using the Report Problem button on the location pin.
Searching by address for me has been accurate (and at least a couple of the screenshots on the linked site are obviously playing on that by having street address in one window and business name in another).
In my part of the world (rural Western Australia) the route mapping (which I use Maps for far more than searching for a business name) is looking pretty good, even though we don't get turn by turn until next month apparently. Incidentally route mapping is something that Google has screwed up for me on more than one occasion as well.