I have used FB customer service in Schipol Schengen Lounge
...and I need to say that it was a quite pleasant experience.
It was to book award for Ms Pinkcity and myself for BOM for next summer ; the award seats were already somewhat booked, and I could easily check the different possibilities, possible dates, etc... The attendant was really helpful and skilled and was able to solve my questions.
I'm now the happy owner of two award tickets for BOM, and I'll visit southern India, return in biz in mid august. Considering the availabilities, doing this by the web tool would have been tough (there is no real availability research tool), and long and uneasy by telephone.
So far, there are no crowds at this office. I encourage you to use it, I'd hate that FB would discontinue this...
Thank to the attendant who took care of me, if she reads...