What's the adoption rate for Vista in business environments? Excluding those companies who outright won't use it, and only including machines that are sold with Vista by default, it seems there is a significant number of companies "rolling back" to Windows XP. According to one particular study, the rate could be as high as a third - which some people might see as a reluctance to migrate.
The other two-thirds, though, tell a different story. According to those who performed the study, they are seeing similar figures in many different areas of enterprises. Even if many of those systems are downgraded, many are being left as-is. What's likely occurring is that a lot of companies are rolling out Vista, only downgrading to XP in situations where they know it is warranted.
Regardless of how you look at it, this is good for Microsoft. It shows people are willing to upgrade, and it shows that Microsoft made the right choice in allowing XP downgrades to continue unabated.