I'm surprised that they were using FF in that VFR corridor- whoever was tracking you there would not only be very busy with commercial traffic in and out of the three-headed monster KLGA/KJFK/KEWR, they'd have all the Hudson River traffic as well: "Traffic is a helicopter; 1 mile at your 12 o'clock, 50 feet, no wait, 100 feet, Piper 1/2 mile at your 9 o'clock, 1,000..."

It'd be like using FF while you're in the pattern at an uncontrolled field, almost.

In that particular zone, the practice is to use that CTAF and keep your eyes peeled.
I generally use FF for legs in excess of 50 miles, or if I'm skirting a busy controlled airspace. I've found that outside of major urban centers, you're unlikely to get anybody if you're below 2500. For my typical trips at 3000 or less among the clustered non-tower fields in this area, I'm better off monitoring the various CTAFs and tower freqs, and keeping a sharp eye out.
But it's a big help on those longer trips- like having an extra set of eyes in the cabin with you. Perfect example would be my epic flight to New Orleans: passing near the Philadelphia Class B at 6500, I was advised of heavy traffic climbing out- not that they're hard to see, but having it called out helps you spot them sooner.
But for most of the 22 hours of that round-trip, I didn't see or hear about any other planes, except in terminal areas where I was landing or departing. Not one! But I stayed with ATC... for the company, if nothing else.

I don't think the majority of "weekend warriors" here in the US make regular use of it, nor do they file a flight plan for that extra bit of "insurance".