It's a few months since RHEL 5.5 was released (march, 2010). Despite this, I would like to point out the major changes and additions compared to the previous release RHEL 5.4. So what's new:
- Kickstart installation - it is possible to exclude package groups in the same way like single packages.
- KVM guests and Cluster Suite - management of KVM based virtual guests with Cluster Suite is supported.
- SPICE - RHEL 5.5 includes components of Simple Protocol for Independent Computing Environments which is competitor for VMware's PCoIP or Citrix's HDX.
- PCI passthrough - physical PCI devices attached to virtual guests are working better.
- Huge page support - it is extended to virtual guests with libvirt.
- Windows 7 support - new samba3x packages supporting Windows 7 are included.
For more details read the RHEL 5.5 official release notes.