A: Each VMware update to ESX and vSphere rolls up many of the bug fixes and other updates that occurred since the last release. Update 1 is no different for ESX and vCenter v4.1.
In addition to the rollup updates, vCenter 4.1 Update 1 now supports a much larger list of databases for storing its information. The new list of supported platforms includes Microsoft SQL Server 2008 R2, SQL Server 2005 SP3, Oracle 11g Standard/Enterprise Release 2, 18.104.22.168.0 or later, (x32 and x64), IBM DB2 9.7.2 Express C (x32 and x64), IBM DB2 9.7.2 Enterprise (x32 and x64).
For ESX, this update adds support for new OSs as guests: RHEL 6, RHEL 5.6, SLES 11 SP1 for VMware, Ubuntu 10.10, and Solaris 10 Update 9. OS customizations are also now available for Windows 7 SP1 (x32 and x64), Windows Server 2008 R2 SP1 (x32 and x64), RHEL 6.0 (x32 and x64), and RHEL5.5 (x32 and x64).
Additional drivers are also added, as well as an increase in addressable processors. With Update 1, there's now support for up to 160 logical processors per host.