Guys (and gals),
I've said it before and will say it again - Islip is getting to be a highly preferred airport when travels have you coming to NYC. Yes, the ride to downtown is a bit longer mileage wise, but if you're stuck in the Lincoln Tunnel during rush hour breathing in those lovely Diesel fumes, you pray for another solution.
Drive time outside rush hour times is approx. 60 minutes to the Midtown Tunnel, 5 - 10 minutes away from Times Square; during rush hour you're probably looking at another 30 minutes. How long is the commute from downtown London to Luton or Stansted - exactly - I rest my case!!
ISP is outside Class B Airspace, so the airport is not affected by delays at any of the other NYC airports - the airport has no landing fees, slots, curfews, and has some of the cheapest Jet-A in the general NY area.
Feel free to PM me for some good pointers if you're looking at ISP - it's well worth a try.