The 1DS is not 10 FPS... It's more of an upgrade from the 5D (Full Frame professional, though the 5D might be better )
I use a 1D MKII ( notice the lack of as S) this is 8.5 fps, and is bullet proof. It would be an upgrade from a 30D/40D (at the time) and is a great camera, I've used it in...