Likely they still are. I worked in several large ad/marketing firms in NYC and they all had very slow adoption rates of new Mac hardware and software because of the cost of replacing hundreds of computers + software. One firm I worked at, with dozens of offices around the world, was still using OS9 three years after OSX was released, and their hardware was older. They had an in-house policy of upgrading hardware every 6-7 years if it was deemed necessary.
Smaller shops may adopt newer technology faster, but, I doubt they are replacing 300+ Macs like the companies where I worked. The only time you see people upgrading every 3-4 years is mostly for personal use or small businesses. But given the current economic climate, many people will likely put off those costs until next year or later once things hopefully turn around.
Also, most of these companies won't immediately upgrade to Snow Leopard anyway until the bugs have been worked out and is proven to be very stable.