Wine-Mono marrys Wine with Mono as an open-source replacement for Microsoft's .NET. With CrossOver 12.0 they began to ship this extra component to Wine, but they decided to stop doing so and only fetching and installing the Mono-based add-on when necessary. CodeWeavers explains their decision to drop Wine-Mono by default as, "the large increase in download size and disk space usage proved too much."
For Linux users, CrossOver 12.1 takes care of an issue running Guild Wars 2 on Ubuntu 12.04 whereby CrossOver was triggering a bug in Compiz that led to a CPU spike. There's now a registry key fix for working around this Compiz issue with CrossOver. There's also a Linux-specific CrossOver fix where the screen would go blank while installing some games.
When it comes to improved application support in CrossOver 12.1, there's fixes for Microsoft Outlook 2007/2010, Microsoft Word fixes, and a handful of Quicken fixes in time for this year's tax season.
For more information on the latest CrossOver release for Linux and Mac OS X, visit CodeWeavers.com.