Look at the last few posts on this thread: http://www.flyertalk.com/forum/briti...deals-j-f.html there are some deals ex-DUB to SFO at the moment.

For more about flying ex-DUB have a look here: http://www.flyertalk.com/forum/briti...ic-thread.html

Nothing wrong with the 757 for a daytime flight though and the preclearance at DUB is a bonus. I tend to fly DUB-JFK-XXX-YYY-LHR-DUB, where YYY is selected based on a long overnight flight on a preferred aircraft.