One of them is my main desktop, and the machine on which I sync all of my iDevices. For my other three machines, High Sierra is officially supported. But once High Sierra was available, I jumped at the chance of getting High Sierra installed on them. For two of those machines they only support up to El Capitan officially so I never bothered with trying to get Sierra on them. I currently have 5 machines on High Sierra. Safari 11 gets some nice upgrades as well, although I believe both Sierra and El Capitan get those benefits too, since they can also run Safari 11. None of this natively possible on any version of macOS prior to High Sierra, yet these formats are the norm now with some iOS 11 iPhones. Now, a 2011 MacBook Pro isn't going to be able to play 4K HEVC of any sort well, but it will be able to play 1080p HEVC just fine, and HEIF Live Photos too, and of course it will be able do display HEIF still photos.

The format support alone is worth it, because no OS before High Sierra can natively understand HEVC or HEIF/HEIC.

This is one of the most important OS upgrades in years, and it runs fine as long as you have 8 GB RAM and SSD. Metal 2 (although this does not apply to 2011 Macs) HEIF <- This is essential if you have a recent iPhone and want to save space HEVC <- This is essential if you have a recent iPhone and want to save space

Mac os sierra on macbook pro late 2011