There are a handful of other bug fixes included, and we recommend that all customers upgrade to this new version, which contains minimal template changes and should be a painless update.
This release of XenForo 1.0.4 follows our principle that third-point (x.x.X) releases should always be more stable than the preceding version, so for the most part you will not find new features in 1.0.4. Major new features will be reserved for second point versions (x.X.x).
Installation and Upgrade Instructions
Full details for how to install and upgrade XenForo can be found in the XenForo Manual.
XenForo 1.0.3 introduced the ability to use the Imagick PECL extension instead of the standard GD image processor in XenForo. However, several customers with ImageMagick installed on their servers were confused that they were unable to use the Imagick option in XenForo.
To be clear, Imagick is a PHP extension that embeds ImageMagick functionality into the language. Having ImageMagick installed on your server is not an indication of the presence of Imagick.
The only way to tell if Imagick is installed is to ask PHP if the extension is present. This will show up as an Imagick block in PHP Info.
To ease this confusion, XenForo 1.0.4 now prevents you from being able to select the Imagick option if PHP does not report its presence on your server.
Templates Changed Since 1.0.3
The following templates have been modified since their release in XenForo 1.0.3.
General Template Changes
The following changes provide functional improvements and fixes or cosmetic enhancements. We recommend that all users integrate these changes into their own templates if they have previously customized them by using the 'revert' controls. If you have not customized these templates, the changes will be automatically integrated when you upgrade to 1.0.4:
Added missing space
Changes to <fb:facepile ... /> to deal with Facebook API behaviour changes
Removed microdata from bottom breadcrumb to avoid issues with Google+ and +1
Changes to Google +1 button to fix various issues , 
Fix logging-out bugs
Prevent resizing of textarea
New class for .ctrlUnit label.unselectable