Much of my work is in the form of contract work for South Africa's 'premium' design agencies, but not 1 of the many project I've done for them has ever allowed for graceful degradation. It must always look and work exactly the same in every browser.
It's not just the agencies fault either, it's their clients that can't see the value of graceful degradation, and why should they ...unless of course it directly affects their pockets. Ideally they should be charged say 30% more - maybe that'll do it