Knowing about CSS Image Replacement and Dynamic Text Replacement, as well as how to implement them, is undeniably valuable. As with most of SEO, having a developer’s skill set (or at least a knowledge of your options), will enable you with a can-do world view. In this case, when a client tells you that they’re committed to a web unsafe font for their headers, and that they therefore can’t use the appropriate keyword rich header tags, you’ll answer “yes you can”.
But there is a very common problem with over-zealous implementation of such SEO tactics without full consideration of their impact. Even SEOs who I have high regard for are victims of this vice. Have a look: