VMware has just released ESX Update 4. You can find the release notes here. I’ve picked a couple of bullets which I think are important, please read the release notes for the other improvements and known issues!

Be sure to also read the compatability matrix, ESX(i) 3.5 U4 requires vCenter 2.5 U2 or higher, and be sure to check if your Hardware Management Agent is still supported.

Newly supported features:

Newly supported Guest Operating Systems:

  • SUSE Linux Enterprise Server 11 (32-bit and 64-bit).
  • SUSE Linux Enterprise Desktop 11 (32-bit and 64-bit).
  • Ubuntu 8.10 Desktop Edition and Server Edition (32-bit and 64-bit).
  • Windows Preinstallation Environment 2.0 (32-bit and 64-bit).

Newly supported SAS/SATA controllers:

  • PMC 8011 (for SAS and SATA drives)
  • Intel ICH9
  • Intel ICH10
  • CERC 6/I SATA/SAS Integrated RAID Controller (for SAS and SATA drivers)
  • HP Smart Array P700m Controller

Newly supported Storage Arrays:

  • Sun StorageTek 2530 SAS Array
  • Sun Storage 6580 Array
  • Sun Storage 6780 Array

Expanded support for the Enhanced VMXNET driver :

  • Microsoft Windows Server 2003, Standard Edition (32-bit)
  • Microsoft Windows Server 2003, Standard Edition (64-bit)
  • Microsoft Windows Server 2003, Web Edition
  • Microsoft Windows Small Business Server 2003
  • Microsoft Windows XP Professional (32-bit)

http://www.yellow-bricks.com/2009/03/31/vmware-esxi-35-u4-released/