Microsoft just released the first Release Candidate of IE 8. Aside from some bug fixes, performance improvements and compatability enhancements, the new version offers a new service that allows you to subscribe to a list of sites that are known to not support IE 8 well. For those sites, IE 8 will automatically switch to comaptabilitymode (esentially using IE 7 rendering engine) without bothering you to switch manually.
You can download the version of IE 8 for your OS here, and read a review of the full list of changes on Paul Thurrott's blog.
One interesting note: for some reason, this version of IE 8 will not work in Windows 7 Beta. Microsoft acknowleged this situation, but did not explain it. If you're using 7 right now (meaning you're using beta 2 of IE 8 that came pre-installed), you'll have to wait for the final release (although I assume it will be pushed on you regardless of your wishes).
One final note: this post was writte on IE 8 RC1. It is much faster, but the text cursor misses the actual text - it's either one space behind or ahead the character I'm typing. I wonder if this is a bug, a feature, or incompatabilty with the Blogger site...