I posted on my blog a small HowTO regarding the way to migrate a XEN virtual machine to VMware Server/ESX. It works out-of-the-box for all the non-LVM disks, and it's been validated over about 7 virtual machines with zero post-migration problems (file system inconsistancy or any other stuff). I know there aren't too many such HowTO's out on the internet (actually almost none) and this should help.
Here's the link:
Warning: this is a highly complex operation and it's not advised to be performed by newbees.
If your virtual machine was organised in LVM disks, you won't be able to start it on the ESX host. Some extra tweaking to convert a disk to a regular type is required, but it works just fine on VMare Server v1.XX
So, anyone interested?? Do I post this tutorial on howtoforge?