The Starkish theme is a stripped-down version of the Zen theme (includes nicer tabs) and a collection of some very helpful extra templating functions borrowed from other themes. Other than that it looks like the Stark theme, that is to say, no theme at all, just plain Drupal output and basic Drupal CSS .
Compared to the Stark theme, it has most Drupal template files (page, node, block, comment) already included, some helpful basic header (ie7, ie6 fallbacks) scripts and configuration variables and separated CSS files already filled in, so no searching for the correct markup in the theming docs.
After having some Drupal theming experience I always revisited this theme, as it is so easy to start upon. Though I began stripping all the tab/crossbrowser CSS of mine, as it seemed easier to fix your own tab styling then to begin with 2 pages eyecandy CSS.
Sadly, there is no Drupal 6 version at the moment.