Opera Mini 4.2 is now official and out of beta. The browser does require a Java Virtual Machine (JVM) to run and is not built as a native Windows Mobile application. However, if you do have a Java Virtual Machine, it's a fine and speedy browser with some upgrades to version 4.1 and 4.0, which is shown in the pocketnow.com review video below.
Opera Mini 4.2 adds some new features including performance increases, synchronizing with notes through the Opera desktop browser, and skins. The versions for Nokia and Sony Ericsson phones add support for YouTube viewing according to the company's site.
To download Opera Mini 4.2, you can visit the official Opera Mini page or point Pocket Internet Explorer (otherwise referred to as Internet Explorer Mobile) on your handset to http://www.operamini.com.