Very much my impression too. I work for an org with sites scattered across the country. My colleagues in Virginia still regularly wear suits, while I in California haven't even owned a suit in many years. For no particular reason I can discern, the gradient seems to be pretty linear. Our Texas people are right in the middle formality wise.
It entirely depends on the industry. Banks, government, defense, etc. will feel very stuffy even on the west coast, while web companies will have greasy unshaven slobs even in Manhattan.
I'm sure that's true, but the interesting thing to me is that it's the gradient exists within an industry too, at least for me in government R&D, we're not at all stuffy out here in the West.