I've been using drop shadows on a logo I'm working with and when I apply the effect it takes a good 30-40 seconds for it to finish, and then same amount of time for each edit. I'm using an older macbook here, so it's not super fast but it's no netbook either. Why are drop shadows so intensive to render, and is there something not quite as resource-heavy for improving logo viewability against a mixed-color background?
The least CPU intestive method would be to copy the art, combine all vectors (or select the layer), apply a stroke or contour of a contrasting color. The vector should apply faster than a raster interpolation. Depending on how old your computer is I would expect if it is older than 1998 (it could be this slow) but if it is, you can probably replace it cheaper than you think. If this is less than 10 years old you may have some serious problems with your hard drive. Or you are working with a huge image?