I did it for the first time last week and it was great fun. It wasn't loaded so I didn't have a neighbour which probably helped in the experience. Note that if you get the dreaded SSSS on your boarding pass you have to go through the extra checks twice, in LCY and in SNN... But if you don't have GE, then landing in JFK as a domestic flight is a delight. There's no queue in Shannon for US immigration.