The old Vista argument which I'm an expert on since I purchased it from day one on release,main issues were lazy companies taking ages to release drivers for Vista,the hardware company in question is responsible for drivers not Microsoft and that goes for any OS.
Also OEM companies shipping their PCs etc below Vista's minimum recommended specs did not help,FUD created etc and there was a lot of that.
I used Vista for good two years including beta games testing for PC game companies,I had no major issues.
I was lucky I had drivers for Vista on day one mainly due to companies of my hardware getting drivers out fast unlike other companies I could mention.
UAC nagging a lot users moaned about with Vista which was toned down on Win7,infact only two things stick out for me on Win7 ie less UAC nagging and some speed increase in the OS,but then we also had faster newer hardware as well.
Win7 had the luxury of two years further refinement over Vista and also had Vista drivers as backup unlike Vista which had no backup on drivers being a new redesigned OS,remember Win7 is based on Vista so that says a lot.
Win7 in many way is Vista SP3 IMHO and I used Win7 from day one until Win8 was released.
You can obviously argue any OS is not at its peak on release but then that goes for XP,Vista,Win7,Win8,Win10 etc so nothing new there,service packs ,updates are there for a reason on every OS.