Although I skipped Vista, I've had enough headaches troubleshooting Vista on relatives and friend's computers, with the vast majority before Service Pack 1 was launched for Vista.
Besides running like a snail (most had 1GB RAM), the main problem I seen was the infamous "Windows Update encountered an unknown error", either when trying to check for updates or install a service pack. On the first few computers I looked at, I tried the System Readiness Tool, "sfc /scannow" and deleting the SoftwareDistribution folder. Both tools took 1 to 2 hours due to how sluggish Vista runs with <2GB and not once have I ever seen these "solutions" fix Windows Update, which only meant one remaining fix - reinstalling the darn OS. :doh: I think I once tried an in-place upgrade (i.e. Microsoft's alternative solution - install Vista as an upgrade over an existing Vista), but all that did was waste about 2 hours as it would fail at the end with some other ".. encountered an unknown error" and spend an hour reverting the whole process.
The only few people I know of that actually liked Windows Vista were those who build their own PCs, since obviously they were not going to fit just 1GB of RAM or install countless resource hogs like the PC manufacturers do. Also, Windows Vista use to intermittently take 5 minutes to shutdown even without installing updates and I wouldn't be surprised if many users gave up waiting and pulled the plug, which probably what was killing Windows Update. I've never seen Windows 7 take longer than a minute to shutdown expect when installing updates.
Unfortunately, I have already experienced one instance of this Windows Update problem with Windows 8 on my own new laptop. After a clean Windows 8 installation, I went through the updates for the first time and after a reboot, it said "Failure Configuring Windows Updates. Reverting Changes.", spending 30 minutes doing so despite using an SSD (I sure wonder what it would take with a HDD.) I tried the Windows Update process a few more times, trying just a few updates, etc., but kept getting this failure message once the laptop rebooted. Finally, I tried Microsoft's suggestions for curiosity (System Readiness Tool, sfc /scannow, deleting SoftwareDistribution folder, etc.), but no luck and in the end just had to reinstall Windows 8. Thankfully the problem hasn't shown up again since.