Just to represent the other side...
I think when the average customer hears "Vista Capable" they assume that it is capable of running Windows Vista. What do they know of Vista Home Basic, Vista Home Premium, Vista Business, and Vista Ultimate - the machine says Vista and nothing more.
Now, had they been branded "Vista Home Basic Capable", then customers would have had a clear picture that their was only one product with Vista in the title that would run on the machine.
THAT is why customers are feeling deceived.
I mean, if you bought a vehicle labeled "off road capable" and learned it could only drive off road on dry dirt paths with no greater than a 15 degree incline, you'd be pretty pissed off when you try to slug through some mud.
Finally, when calling all these people idiots, remember the Dilbert Principle - once we realize that we all have times when we are incredibly brain dead and stupid, then maybe we can learn to sympathize with others rather than condemn them.