Well, it's not as impressive as could, but it's a start. We know that writing refactoring tools for C is difficult, as with the preprocessing a C compiler can be made to understand virtually anything. Doug mentioned their struggle when he commented earlier on this blog. Good news is that it's now easier to start using Eclipse for C projects, as it is possible to get Eclipse and SDK in same package.
We have been using SlickEdit for a while. Slick has a bit more refactorings for C - actually all three of them.
Refactoring is an important ingredient in test-driven development and while these tools are not much, they still take the bar for quick refactoring lower.
And that is good news. If you are not able to decide from this myriad of choises, you can choose the middle way - get the SlickEdit plugin for Eclipse.