We're a bit more cautious than you @kevinrm despite us having a much simpler store setup
Our Dev Store 5.2.17 upgrade was was indeed smooth and easy, just like you said. There is a teeny glitch in the verification check though, as prior to submitting the upgrade, we got a caution type notice saying that a file had been 'modified' On close inspection, it's because the upgrade is adding a new file that wasn't there before and actually has no XC5 purpose. The file that XC5.2.17 identifies prior to running the XC5.2.18 upgrade and then adds, is this one:
It's part of the TinyMCE integration module upgrade. This DS_Store file is just an OSX Desktop Services Store file that has been carried over from somebody's OSX desktop at XC, so it's not a big trauma. It has zero effect on the upgrade, but you do have to go and delete it off your server afterwards. A slight correction before the merchant wave is released would be handy for people. We'll be upgrading our live store to 5.2.18 in the merchant wave. Meanwhile, the 5.2.18 version on our dev store runs with no faults or imperfections which is nice!
We are going to wait for the merchant wave release of 5.3.14 too, as that upgrade (on our 5.2.18 dev store initially) will be a big learning curve. We have all our customisations / alterations contained within /skins/custom_skin and all these must be converted to twig manually... much coffee & patience
One question? Are you not running 220.127.116.11 on PHP7? That should definitely add some processing speed too. Once the merchant wave is released, we can and will run our 5.2.18 live store on PHP 5.6.23 and our 18.104.22.168 dev store on PHP 7.0.8 with the config change made via .htaccess. Maybe you can do the same?