SF,
True for the expensive specialist market GPS kit, but not for handhelds or commercial aviation GPS sets, which still just use time and distance to compute velocity.
I know that G (and a fair few other light aircraft FT people) use relatively cheap commercial GPS sets that don't use doppler velocity correction, hence my post pointing out the potential errors.
Having just looked at the specs for a few relatively top end commercial GPS receivers, I noticed that they haven't yet chosen to use doppler measurement in the main. The main growth area for these specialist sets seems to be in the race car instrumentation market of all things.