Yeah, when we got off the plane at Heathrow, having connected in Shannon, we just walked off, picked up our bags and that was that. Everything we went through in Ireland seemed to have done the trick. This was despite the Aer Lingus woman who chedked our bags in Boston, and knew we were connecting in Shannon (becuase she put the "Transfer at SNN" tags on our bags), telling us we would go through customs and immigration in London. We went through something fairly quick in Shannon and that was it.

Even with pre-clearance on the way back (from Dublin to Boston) we had to hand in a card to an immigration official in Boston.