Different doument types, different work flows
I also like my design artifacts to look good, even if I am the only person who sees them. Two highly recommended tools are AbiWord and OmniGraffle because their default file formats are plain XML text files.
I admit that disk space and network bandwidth are close to free now but I still like to keep a project directory small. By using design tools that have small file footprints, most projects (source files, build scripts, tests, and design artifacts) are small and tidy.