The update also addresses a number of security issues, including one related to a vulnerability in libxml2 which could lead to crashing when parsing maliciously crafted XML content, and another related to a vulnerability in the way Safari initiates navigation via the “Open Image in New Tab” option that could disclose local information. Also fixed are three other vulnerabilities related to how WebKit implements Cross-Origin Resource Sharing, handles FTP directory listings, and behaves when encountering an HTML 5 Media Element that points to an external resource. The update is available via Software Update or from the Apple Support Downloads page. (Free, 28 MB)
Maybe it's just under the Japanese system, but Safari 4.0.4 binds option-command-"1" for the "View Top Sites" menu item. It used to be shift-command-"1" in Safari 4.0.3 and before it. Such kinds of key combination tend to be used as system-wide hotkeys, it is _totally_ annoying that Apple changes the key combination silently and arbitrarily. (I know that it can be changed via the System Preferences panel, though.)
It still doesn't have a true equivalent to Firefox's multiple-tab home page option. I realize there are ways to get something close to a functional equivalent, but what is REALLY needed is what Firefox provides, i.e., a Safari "Set to Current Page(s)" option that will replace the current "Set to Current Page" option.