Microsoft listed seven major improvements in IE8 beta 1 that developers are interested in on the MSDN IE blog, including full support for CSS2.1, support for HTML5, and built-in developer tools. Beta 1 is mainly provided for developers to experience and use, while ordinary users would be more suited for beta 2.
The article also mentioned that German and Simplified Chinese versions of IE8 beta 1 would be released shortly, but no specific date was announced.