Microsoft has released the final IE9 Platform Preview and the Beta is scheduled to be released next month. The interface of the Platform Preview is just a shell — in order to open a Web page select "Open…" from the "Page" menu — but the performance is impressive. The latest release scored 95 on the Acid3 test and everything seems to work on the sites I've tested. You can install the fourth and final IE9 preview here. It installs as a separate application and won't overwrite your current installation of IE.