They aren't timed well, IMHO, to connect to as many p.s. options as I'd like, nor is there much frequency. You can't connect to the earliest few p.s. departures, as the first IAD-JFK RJ flight gets in at 9:40am or so at JFK. Sucks that there isn't a 6:00am or even 5:30am ex-IAD departure to JFK.

Sometimes, when making the WAS-JFK-SFO/LAX trip, I take the US Shuttle ex-DCA, codeshared with UA, into LGA and then catch a bus or take a cab over to JFK. It's often cheaper (sometimes quite a bit!), but then, even catching the earliest shuttle flight of the day, you still can't expect to catch the first or even second bank of p.s. flights outbound--you're stuck with the lunchtime flights any way you cut it, unless you fly up the night before.

A 6:00-ish ex-IAD flight to JFK would at least let you catch the 8:00-ish p.s. departures.