Are editorial management systems helpful to journal editors?
I served as editor-in-chief of an IEEE magazine for 4 years and have been an associate editor on various editorial boards for the past couple of decades.  For as long as I've been on edboards, I'd say they have used some flavor of online management system.  Pretty much everything I'm on now, not to mention everything I submit to, has coalesced on "manuscript central" from Scholar One.  

I fully agree with @Nate Eldridge's comment about the "paper" trail.  That is definitely a plus, because I can look and see past correspondence -- was someone reminded at the right time, etc.  And to be honest I couldn't imagine managing this offline.

That being said, I find the system (and the others I've used) frequently painful.  Aside from the bug about being negative days late, my biggest problem is that the system tends not to remind anyone that a task is outstanding.  In particular, as an associate editor my job is to line up the actual reviewers.  In two cases recently, I discovered that I'd invited 3 people, and usually more (as people might decline), but in the end 2 from each of 2 papers had agreed to review and 1 in each case had never responded.  The system sent them a reminder or two, then from what I can tell, it neither reminded them nor told me it was time to find someone else!  

There are other minor difficulties, such as finding reviewers within the system rather than creating duplicate accounts for them as new reviewers, that sort of thing. 

Bottom line: they serve a purpose, but they can be improved.  



Are they helpful to journal editors?

Absolutely.

Can they be improved, especially from the standpoint of reviewers?

Absolutely.

But don't throw the baby out with the bathwater.