I just recently wrapped up a project utilizing customized Twitter Bootstrap / CSS3 / HTML5 and I was pleasantly surprised at how smooth everything went between IE/Chrome/Safari/FF. This is the first time, in a long time, that everything just "worked."
Oh and the fun that is working with native iOS, Android and WP browsers.
Then put on top, whatever web framework might be required by the customer.
The fun starts when the UI isn't working pixel perfect to those Photoshop mockups or the cool HTML 5 effect that can only be partially implemented in all browser versions mentioned in a "Request For Proposal".
If they would like to create 20+ different mockups and supply them to me I'll gladly do it for an exorbitant sum money, but otherwise they need to realize that the relative fluid nature of the web and it's many form factors is going to preclude them from getting that pixel perfect design.
Then all of that flies out the window because we have that one asshole manager who promises the world and ensures it will be delivered yesterday :)