Tera_firma
I guess it's a case of whether you want a cheap flight , cramped seat and a journey that take's twice as long as a direct flight.
I've been twice and went with Virgin both times from Manchester for about £500 which was probably upto £100 more expensive than other flights but without the hassel of changing and sitting in another U.S airport for upto 4 hrs at a time.
It's not too bad going but coming back is a killer, it's just not worth all the hassel for an extra £100, loads of leg room (747), good looking stewardess's , free booze ( got picked up the other end !!)
Next time though i'm going for the fly drive option ,About £600 for flight with Virgin and 2 weeks car hire.
Good luck and have a great time !!