To me It is a very good update: system stability and speed has been much improved. It seem that user interface has been optimized too. Infact, After the rom update I did a system restore. On reboot, the UI manager asked me to upgrade user experience replacing "traditional" android on screen key with gestures.
After a short time of adaptation, I find now gestures very useful.

Anyway, I think that who blames because of android version not being updated, misses the point: you have not buyed a vanilla android phone. You buyed a flymeos one, which already has a very own set of functions added to vanilla android one. You shoud ask to you, when comparing meizu phones software to other vendor's android implementations: "Am I happy with this functions?"
A different thing are security updated. On this point I agree  that meizu shoud improve the frequency of releasing such type of updates and support its phones at least for three years.

The android version can be a limitations just relating to apps compatibility. And, for what I know, on this point there are no compatibility issues at all.

hope they'll give us the Oreo upgrade soon .. Flyme upgrade only isn't enough