Just a side note on demo performance... there seem to be definiate bugs with the engine that mess things up. To get better performance, turn "Bloom" on and set sampling to about 4x or so (yeah, I know... antialiasing increases performance... that's pretty messed up). Also, go for "standard" resolutions.
That said, I think the graphics are pretty sub par even when it's running smooth at 1024x768 4x AA and "bloom" (that just seems to make it fuzzy...). I'd blame the texturing... it seems fairly ugly and repeditive.