we almost always fly through JFK - it's not the easiest but not the worst either..
the air train is relatively painless - make sure that you're actually on the air train and not the regular train, which comes by to the same stations...
every time i use that air train, i ask the airport worker about a thousand times to make sure i'm getting on the air train.....no way do i want to end up in the middle of queens somewhere...
you can tell the airport worker you need to get to terminal 8 (i think that's the American Airlines terminal) and he/she will direct you to the train.
terminal 8 has the longest line for security you'll ever see....ever ever ever.....if you see that you're running late, tell the TSA person in charge of the line that you're going to miss your flight and they'll push you to the front...usually....(with a lot of nasty looks and comments from the new yorkers)...
i've never landed in terminal 7, so i can't tell you anything about it...
but i've flown in and out of terminal 8 a number of times...
oh...another thing to know about JFK immigration......if your international flight is arriving late tell the cabin crew on board the plane - they will notify immigration on the ground who will be at the plane to give you a fastpass to use at immigration. Of course, only if there is a long backup at immigration and only if you're within about 1 hour of your flight. It's really quite magical. We experienced that last year for the first time. We were given this big orange fastpass which lets you into a special speedy immigration line. that was because our flight was almost two hours late and there were lots of people on board who were about to miss their connecting flights.
once we were through that and customs and dumping our luggage back at the connecting desk, we made a mad dash to the air train to get over to terminal 8 and then almost missed the flight because of the security line, but were then pulled through there and made it with about 5 minutes to spare
it's not a bad airport, just a HUGE and very busy one.
the AA terminal is nicer than most of the others.