Make sure you get ticketed
I have now been through the whole process twice: First the SEA-LHR-MAD trip I posted earlier, and then a rebooking to SFO-(SEA-LHR)-LIS after Labor Day for $440 :-). Three data points in case they're useful:
* You can force great routing using ITA Matrix and bookwithmatrix.com will ticket on aa.com
* BCN was almost as cheap as LIS but it can be rainy in September
* The EXP desk agents are very nice and hard-working but this is a new process, and the certificates did not get pulled properly for either itinerary. If AA.com shows your tickets "on request" after a day or two, call them back.