Your the one that mentioned it first :/ let’s not get off topic though and also I was saying PMMP is better!
I don't think there has ever been what the pocketmine team would call a 'stable' version of pocketmine since it began, simply because they are permanently catching up with client updates. As the very name ALPHA indicates, the devs do not consider it stable - but the tagged ALPHA8 release is the recommended version. More important than whether pocketmine itself is stable is whether or not the API is stable, because that is the only way you can ensure your plugins work, and don't break... Since alpha8 was tagged this gives plugin developers something fixed to work against - if you update to alpha9 before it is tagged then you'll have to use unchecked builds from Poggit, and monitor every plugin as alpha9 evolves...