I am surprised that they chose East Coast over VWC. The 390s have been fully vinyled before and looked okay, plus they stay in a single set.
I am surprised at the genuine hatred for this livery on some other fora. It gives the railways a good boost and shows that they are still considered relevant. I would be keen to see more advertising liveries in future.
It's the renumbering that makes it look like a silly stunt. I welcome a bit of variety in the livery (and will make a point of trying to get a picture of this one) but renumbering it back to a 91/0 is a bit pointless. I have a feeling they would have gone for 390007 (remember Virgin had a Superman livery for a while), but of course the ICWC franchise is still not sorted, so they want this around for a while.
Of course, a Jubilee Line, or maybe District Line, unit might have worked as well.