I have actually 'plugged' VMware on the config restore process. For ESX/i 3.x....yes, you can do that, but for 4.x it's not because of the the new architecture in 4.x. I don't know why it's so hard, but they have as yet to provide me with the files that need to be copied then restored for 4.x version.
I would agree with you on keeping with ESX...I certainly am (and I just like it better...I like the COS and not CLI). My recommendation is that...stick with ESX until VMware 'forces' folks to ESXi. By then, I'm most certainly sure they will have a b/u process for ESX configs. You can use update mgr so you don't have to go through all the reconfig's; but me personally I always do 'fresh' installs. I trust that more than upgrades. I don't mind going through the reconfig's. It gives me a chance to relook at things and verify things are done properly.
Regards,
~coolsport00