Ads. Mostly for Microsoft stuff that I don't and will never want. That alone is fairly bad. Even after spending a bunch of time fixing the OS there were still a few. Privacy concerns (ditto).
The updates are a real problem, just all around. Final straw was when one added Outlook back to my start menu.
For all this I got an OS that, actual objectionable things aside, is less pleasant to use than Win7. I'm out. First time I haven't had Windows on something since 3.1.
[edit] by "added to my start menu" I meant "pinned to my task bar"
What went wrong for you?
My biggest problem was that I had to turn off Defender because it was causing some delays with the real time scanning.