CRM 4 Mobile Express Goes Gold with Update Rollup 5
The official blog post: Product Release: Mobile Express for Microsoft Dynamics CRM 4.0
Mobile Express for Microsoft Dynamics CRM 4.0 is available as a free download and supports the product's full customization and multi tenant capabilities. Those capabilities allow organizations to deploy a CRM solution for one set of workers and, using the same software licenses and hardware, develop instantly mobilized xRM solutions for a wide variety of other business needs using point and click tools.
Keep in mind that the Mobile Express client installs CRM Update Rollup 5 as well so make sure your applications have been tested before deploying:
Downloading and installing Mobile Express for Microsoft Dynamics CRM also downloads and installs Update Rollup 5 for Microsoft Dynamics CRM 4.0 (KB 970141) on your server, a tested, cumulative set of updates for Microsoft Dynamics CRM 4.0. It includes performance enhancements that are packaged together for easy deployment.