Electrons confined in solid state devices of various kinds
display very peculiar properties that continue to attract
the attention of experimental, theoretical and computational
physicists alike. I shall discuss recent progress in the
modeling of two-dimensional  electron systems of exceedingly
high mobility, as realized in quantum wells and field-effect
transistors, concentrating on the spin susceptibility.
The two--dimensional electron gas embedded in a a uniform
neutralizing background, once important details of the device
are properly taken into account,  is capable to describe
experimental evidence.  I shall argue that the extremely
accurate treatment of the intereaction provided by the
Quantum Monte Carlo method is crucial.