I love Windows 10 - really! I was using a Windows 10 laptop at work with the RC version - beta
testing - some minor issues that they worked out as they got closer to
release date. I upgraded my laptop first a couple of weeks ago, no issues. Then Sara's computer last weekend, no issues.
Yesterday I updated my main system to Windows 10 - wonderful, very few issues and those are due to older software.
One thing to watch for if you use Fences - the free version is NOT compatible with Windows 10. The issue is that you cannot drag icons around on the desktop anymore. The work around is to cut and paste the icons from where they were to where you want them on the desktop. That works fine. Also, if they are in a fence, you can move the fence.
So overall I recommend upgrading to Windows 10 ASAP - if you have windows 7, 8 or 8.1 it's free, but only until July 2016.