Mostly it's here to replace the affine transformations in the System.Drawing namespace to allow for graphical transforms without having to rely on System.Drawing, and by extension GDI and GDI+. This is a good thing as the CLR makes it onto platforms which don't have GDI+, and as better technologies like WPF become established.
Other than that, .Net has potential to be very powerful for numerical processing. It mostly hasn't lived up to this potential, which was even seen early on
. However, if the JIT improves to the point of being able to take advantage of SIMD extensions to modern CPUs, or general purpose GPU computing (GPGPU), then the possibilties become dazzling. NPack could be a project to explore using these computation resources.