ET keeps writing things like:
A hand-held GPS just does not seem to be the appropriate tool
may not be accurate for this job.
There's a whole lot of "may be" and "seem to be" statements in your posting. Yet, no facts. If you don't have the facts on GPS, how 'bout you go educate yourself before casting unsupported doubts on Vmax. THere's plenty available on the web. I don't think it's Vmax's responsibility to make up for your lack of knowledge about the system.
If we were arguing about a couple mph, there might be some validity to the whole "walmart/civilian/consumer GPS" argument, but there isn't as it's obviously accurate to those limits and Vmax has the repeatability to show it wasn't a fluke "bad signal".
Selective availability is indeed off so all of the "intentional inaccuracy" arguments are also invalid.