~ 25 FPS average with Pentium 3.0 Ghz HT w/ 2Gb Ram , GeForce 7800 GS 512 Ram.
I had about 465 entities visible at once in some places which gave me the worst frame rates (~ 19).

In my opinion, the ground is much too light (especially the grass and shadows),
and the sky is a little too dark. Also the vegetation is a little too light and
mostly the same color. These things create low contrast and a washed out look.
But maybe thats what your after?

Not two, not one.