You won't be disappointed.

A word of caution. 8DEF are great seats, and on IAD-SFO this should not be a problem--BUT on long-hauls, if there's open space, the F/As realize these are great seats so they'll try to re-seat a few sporadic passengers in the rear C cabin so they can have 8 & 9 DEF to themselves. I saw this on an ORD-NRT once as I was in 8J. I started to get a little apprehensive, because there's no way I'm giving up my 8J!

Since IAD-SFO doesn't require a rest for the F/As, plus with the fact that these are heavily-loaded routes with tons of upgrading 1Ks, 1Ps, etc., I'm certain you'll see the entire C cabin full.