Last time I flew into JFK on an RJ from IAD we arrived right where my flight to VCE was taking off, so it *could* be okay.
Granted, my flight was delayed an hour or so (padded time included (the 45 minute flight was scheduled as I think under 2 hours)), so I get off my plane only to find that JFK-VCE was just about to begin boarding...so the more hours in JFK, the better.
DD