The lounges are much nicer now than they used to be and the one I camped out in the other night for a few hours was WAY nicer than the terminal. Some photos (including the bar menus) are here.

Still, I'd really try to find something else to do for the 6 hours I think. That's a long time to spend in any lounge, especially a domestic one. If you're light on baggage you can easily spend a few hours in Manhattan for less than the $50 admission fee to the lounge. Even the Oasis lounge - which is much nicer than the SkyClubs - would try my patience after a couple hours.