All hat and no Cows? Not heard that one before. Check out the Vauxhall Ampira which is the UK version of the Volt. I personally think it looks nicer - more a cross between the Volt and the Honda Insight.
It may be a western USA, idiom. There are two types of Cowboys, One has cattle he herds, the other just wears a cowboy hat and poses. I said it wrong, I should have said "All hat and no cattle." http://en.wiktionary.org/wiki/all_hat_and_no_cattle Volvo did not pose, it just made a electric car. GM talks about a theoretical electric car it may make someday, but so far it is all posing.