One note about the caching, we have a new feature coming in the next release where there is a guid passed as a parameter to the css handler url, and there is a button under Administraion > Advanced Tools > Designer Tools > Cache Tool
that allows re-setting this guid, doing that effectively "clears the cache" for all users because the browser cache is based on the url and since the url changed due to the guid changing all visitors load the latest css after the guid is changed even if they had previously cached the css in their browser.
Previously my advice after making changes to a skin was to rename it to achieve the same result but this guid makes it much easier especially when using different skins on different pages where it could be tedious having to rename all the skins in order to make sure that visitors got the latest css.
you can see this currently on the demo site.
Best,
Joe