My experience...
1. Don't try to call IIO unless there is very very valid reason like to confirm address change, your RD is far behind ( 1 month back from others) etc.
Calling IIO will be tracked and they note it as well. And I am sure one wil get Query defenetely if they call more than once. I called 2 times and they send me a query 'Employemt update' (got doubts on my call) and ofcourse, it got approved within 2 weeks after that.
2. Its not that IIOs are not knowledgeble, they know but rememeber you are calling the same INS # for all cases that means any IIO who picks up the phone shall be able to answer any case details and not just I485. So, some IIOs who knows about I485 very well, may talk well but you can not expect all the same (with so many types of cases INS have).
When I called IIO on Aug'15th, they said my case was not still assgined to any officer and it may take 3 months for approval and on the same day evening I heard on AVM that an RFE is issued.
So, this example may clear your doubts on how effective IIO information is useful.
Best of Luck to All