Updates are already available for Internet Explorer 8 for Windows 7 RC which address a performance issue with the browser as mentioned in Microsoft Knowledge Base Article 970858.
Windows 7 RC includes a feature in Internet Explorer 8 that helps users recover from unresponsive Web sites. This feature uses a timer to detect when a Web page has become unresponsive. On low performance computers or on computers under high load conditions, the time-out value is frequently exceeded. Therefore, you frequently receive the error message that is described in the Symptoms section.
I’ve personally found Internet Explorer 8 to perform somewhat better on some websites after this update.
Another update to the Compatibility List View is available although that applies to Internet Explorer 8 on all Windows versions unlike the other update. Both these updates have been pushed through Windows Update so don’t forget to check for them if you have automatic updates disabled.