I'd just like to point out the footer that comes along with emails submitted to Plesk support:
SUPPORT ESCALATION PROCEDURE
We stand behind our product.
If there are serious problems that are impacting your business and you are not getting help through normal channels, contact:
Pavel Malyavko
SWSoft Support Manager
+1-703-995-4157
pmalyavko@sw-soft.com
Mr. Malyavko will escalate the problem to either the Director of Engineering, Director of Application Development, or the CEO.
I must agree: Plesk has been proven as one of the most stable and "just working" control panels. I used it flawlessly for years, and upgrades went great. Unfortunately, due to a very small flaw (that could have easily been fixed) in the upgrade to Plesk 8.0, it completely crashed my system. Keep in mind that I did wait about 3-4 months after the initial release to upgrade. I did end up getting it back up and working though after long hours of analysis.
In Markus' situation, I do believe there has definitely been a lack of competence in server management. It is up to the system administrator to secure the server and lock it down, and it's quite likely the attack could have been prevented. I recently tested my full-server backup on a fresh box, just to see if it worked, and there were problems with it that just as you described. I was able to resolve the problems on the server and get a fresh-working backup.
Just like security is a process, so is your disaster-recovery plan.
However, I can also agree that there are a few aspects that are extremely buggy and require more focus in development. Those being:
A) Pleskbackup/restore utility
B) Testing
Personally, I wouldn't care if Plesk stopped adding big new features to their control panel and decided to address more focus on operability, stability, and working on resolving bugs. To me, that's what I look for in a control panel. In reality, those are the most important factors in choosing any piece of software.
Simple rule -> when you run a server, you need a knowledgeable administrator to manage it, and that's what keeps people like me in a job. If Plesk locked down your system for you, they would have more complaints about software not working, or other related problems. Security is a customized implementation; you don't just install software to do it for you, it has to fit your working scheme.
Sometimes completely putting the blame on someone else and "It should have worked." isn't the greatest attitude to put towards disasters that are all something you could have avoided yourself. In my opinion, Plesk IS at fault for the backup problems, but not nearly as much as you are.
Limedrink.