I've done some extensive testing with Vanguard. It seems the engine doesn't like bloom and HDR enabled together, although it lets you do it when most games don't. Bloom gives it an extra glare effect off concrete surfaces and around light sources, but for the most part there's no visual quality increase and it makes ~10fps difference. In populated areas with lots of NPCs, it's made up to a 15fps difference by turning bloom off.
With a single 8800GTX, SLI disabled, v-sync enabled (capped at 60), all in-game settings maxed:
For the most part it stays pinned at my refresh rate. This part was a little more demanding, graphically.