I got the brake mounts faced last week, finished getting everything adjusted, and put 80km on the VB-R-218 over the weekend.
I'm not going to make any claims that I'm the most discerning rider, but I haven't found it to be sluggish or harsh. The final ready-to-ride weight[1] comes in at a whopping 9.945 kg, a full kg heavier than my Giant Defy and 1.5 kg more than my Canyon Ultimate in similar configurations, but it feels snappier than the Defy because of the steeper head angle, and is just as much fun as the Ultimate. If I hadn't seen the numbers on the scale, there's nothing about the ride that would make me think I'm riding a battleship.
My only complaint so far is that I decided not to wrap the cables with foam -- I've never had to on my other bikes, so I decided to forgo it with this build as well -- and that was a huge mistake. On the first ride the noise was distracting, but on the second ride I was more used to it. The internal cable routing was enough of a pain that I'm not going to take it apart to wrap the cables, but once the cables snap and I need to replace them, I will be putting in foam liners.
[1] Ready-to-ride includes pedals, saddle bag with repair kit, bottle cages, Wahoo, and lights, but not the water itself.