We did this update last Thursday, our system is still offline, that's 6 days now. Vital deamons wont start up anymore,.. actually, pretty much nothing wil work. Plesk doesn't even start up. Can't even SSH into the box. I had to use Webmin to be able to get to the files on the old box.
It seems that every update screwed up something new. I am seriously getting sick of this product. This is costing us huge amounts of money. We had to purchase a new server, pay for engineers to get the data transfered to the new box. And now still nothing will work because the new box doesn't have 9.0.1 but 8.6.0, and it seems the hosting company doesn't want to upgrade to 9.0.1 (geezzzz,.. I wonder why!!)
We have used Cpanel in the past, and even just Webmin. Not as "user friendly", but 1000% more reliable. Sure, we have had a few issues with Cpanel, but nothing remotely close to the huge list of problems Plesk has thrown at us.
Plesk has turned out to literally be a Killer App. Avoid this update,.. and if possible,.. avoid this product.