Based on my experience in Atlanta DO (which may not be true for all), it was not very useful. AFAIK, They are not true immigration officer but immigration information officer. They do get to see screens but may not be same as what IO can see.
In my case, I had submitted a request to my IO via infopass to change my oath from administrative to Judicial so I could change name. It never made it to the file and my IO never responded. I made another trip and person at infopass lied to me about my name that will appear on the certificate. He also told me that my record is in "oath to be scheduled" stage where as oath date was already fixed. (I received oath letter next day after I got back from infopass. The letter was dated more than a week back)
In both cases, I got different officers who both yelled at me and were not courteous (Though the officer in the window next to mine was very helpful to the lady in that window.)
Having said all that, 800 number also may not have all the info unless you can escalate your inquiry to their superiors. I have read that supervisors at 800 number have more access to your records.
I do not think Infopass can expedite your case.
Sorry to be negative. Wish you good luck !!!
