One thing that I've found frustrating as a web developer over the years is the work flow between design, css layout, and programming.

Typically the workflow (from my perspective as a programmer) will go something like this:

1.  Designer creates layout in Photoshop.

2.  CSS/HTML Guy cuts up design. 

3.  Web developer inserts dynamic content, ajax.

Sometimes I'm the CSS guy, sometimes I'm not.  I've never been the designer (at least not in professional situations).  The most friction is between the design phase and the css/html phase.  If a slice contains errors, a new one must be requested from the designer.  Turnaround times can vary, but usually there is an interruption to the work flow.  Common causes of errors are slices that are not suitable for use with CSS tricks such as repeating 1px vertical or horizontal gradients, images related to rounded corners that are not formatted correctly due to transparancy issues, etc. Communicating the exact requirements necessary for image slices to the designer can be time consuming as well.

So, in order to solve this problem and speed up development, I've taken some time to learn the rudiments of Adobe Fireworks.  With Fireworks, I can import a psd and retain all of the layer and textual information.  In this way I can make my own slices without the turnaround times required in requesting them from the designer.