When designing wireframes, content place-holders are good. However, displaying actual sample content and data (de-identified if necessary) is always better. This gives an idea of how elements on the page blend with each other and "calls to action" can be placed appropriately. Take into account which content goes where and how much will appear. Don't leave content until the end, it does have implications for your design and layout.
Suggested by Isaac Sane http://force10x.com/blog/