We just converted 3 of our virtual machines running on Virtual Server 2005 R2 to VMware ESXi yesterday and it went pretty smoothly with just a couple of minor issues.

The first issue is the mouse cursor not working in VMware console after installing the VMware tools. The fix is just a simple registry edit:

1. Open Registry Editor (regedit)
2. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4D36E96F-E325-11CE-BFC1-08002BE10318}
3. Double-click on UpperFilters and delete msvmmouf.
4. Reboot the VM.

Source: http://www.petri.co.il/forums/archive/index.php/t-19387.html

The second minor issue is when you try to set the static IP address to the same IP address before it was converted, you might receive a message similar to this:

The IP address XXX.XXX.XXX.XXX you have entered for this network adapter is already assigned to another adapter Name of adapter. Name of adapter is hidden from the network and Dial-up Connections folder because it is not physically in the computer or is a legacy adapter that is not working. If the same address is assigned to both adapters and they become active, only one of them will use this address. This may result in incorrect system configuration. Do you want to enter a different IP address for this adapter in the list of IP addresses in the advanced dialog box?

This is probably not a big deal, but if it bothers you just do the following:

1. Click Start, click Run, type cmd.exe, and then press ENTER.
2. Type set devmgr_show_nonpresent_devices=1, and then press ENTER.
3. Type Start DEVMGMT.MSC, and then press ENTER.
4. Click View, and then click Show Hidden Devices.
5. Expand the Network Adapters tree.
6. Right-click the dimmed network adapter, and then click Uninstall.

Source: http://support.microsoft.com/kb/269155