Well, my tuppence is glad to know you get a plane with a decent IFE but hey i always fly economy or once in a while PE so a good IFE can make a difference.
Been flying back and forth for 19 years (afraid to say been lurking on this forum for years and only recently joined) as my partner is based just outside dc.
My October trip is my 47th time ive flow out there on either BA/UA/VS
ive had great, mediocre and down right p... Poor flights from all 3 airlines that serve LHR to IAD dirctly
ive also gone locally via Paris and Amsterdm. Ive got delayd due to snow and an (in)famous Air France strike.
The 343/346 journeys i have taken have ranged from great to pants.
ive had super clean planes to filth ridden planes. v(
ive had VS crew who were stunning but lousy customer service skills

to non model esque but couldnt do enough for you the entire flight. ^)
My ipad is my new best friend but im looking forward, having flown EK and SIA and enjoyed their systems, to know finally an on demand system will be standard on this route.
Im flying out in october pre the change but coming home on 28th so 330 it should be. Th march and april 2013 ahould be 330 both ways.
What do BA and UA have to offer - old 747/767/777.
I for one am excited to fly a different plane. I lookbacknowandthink what a wow moment i felt to step on board a newish UA 777 when they debuted on the IAD/LHR routeandhope to feel the same in October On the 330.