Same here, I get basically playable FPS in NYC but over London my rig suffers.
Also, I am not impressed with the photogrammatry at all. I have fiber and 1GB connection. The scenary still does not load in properly and one second it looks great, look in a different direction it looks like a poor import from Google maps, except those look better.
It is not conosistent, I prefer regular textures. it just does not do it for me. NYC photogrammetry is much much better. From a distance it looks like pre 1940.