Fancy new tricks made possible by newer browser versions is a great tool to improve the user experience. However, not all browsers support the same features.
According to a recurring theme from the Future of Web Design conference in New York, that's ok. What matters is that the user experience remains the same. Fonts looking different or windows not having rounded corners do not necessarily affect user experience. So the struggle web designers go through to make the interface look exactly the same in every browser might be a moot one.
As long as the focus remains on user experience, its ok for the website to not look the same in every browser.