After you cold migrate you need to upgrade hardware and VMware tools on the VMs. Might want to swap steps 4 and 5 just to be safe. Would hate to accidently destroy one of your VMFS partitions on a LUN.
fyi...here's some good reading material for upgrading....
Upgrade from ESX 2.x to ESX 3.0:
Virtual Infrastructure 3: Beta to Production - http://download3.vmware.com/vmworld/2006/mdc5173.pdf
Understanding Virtual Infrastructure Upgrade Moving to the new ESX 3.0/VC2.0 Release - http://download3.vmware.com/vmworld/2006/tac9809.pdf
Details of What's New and Improved in VMware Infrastructure 3 - http://www.vmware.com/support/vi3/doc/whatsnew_esx301_vc201.html
Vmware Infrastructure 3 Release Notes - http://www.vmware.com/support/vi3/doc/releasenotes_esx301_vc201.html
Planning a Upgrade to Vmware Infrastructure 3 - http://www.vmware.com/pdf/vi3_upgrade_plan.pdf
Vmware ESX 3.x Server and VirtualCenter 2.x Upgrade Guide - http://www.rtfm-ed.co.uk/docs/vmwdocs/ESX3.x-VC2-upgradeguide.pdf
Upgrading your VI2 to VI3 - http://www.vmware-tsx.com/download.php?asset_id=25