I upgraded all three of my machines to Win 10.
All were Win 7 before, but all were set to automatically update anyway. I found that to be the easiest. It got tedious manually dealing with updates.
Initially last year I wouldn't have recommended it for most people because there were way too many bugs with Win 10, and some applications were not supported, but the bugs are much less in 2016 and application support is better.
In my case my VPN app was a bit odd in Win 10, but worked with a simple workaround and all my other applications are supported fully, so I felt comfortable upgrading. The only issue is I lost Windows Media Center on one of them, but oh well.
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OTOH, I'm stuck on old OSes for some of my Macs. Core Duos are acceptable performance-wise for surfing, but my Core Duo iMac is stuck on the obsolete 10.6, which is problematic for security and browser support. And my Core 2 Duo MacBook is stuck on 10.7.
My MacBook Pro will lose support this fall, and will be stuck on 10.11, but I'm optimistic I can run a hack to bypass the check to run 10.12, since it actually has the right hardware. My Core i7 iMac will probably lose support in a couple of years.
However, I just bought an encrypted hard drive and it works beautifully in 10.6 and 10.7 (and Windows 7 and 10), but it is problematic in 10.11. Who knows when this drive will be fully supported in 10.11, and 10.12 with comes out in a couple of months.