I successfully upgraded by Dell Precision 390 (not on the HCL) from ESXi 4.0 to ESXi 5.0 with no problems during or after the upgrade. However, I did receive several warnings during the installation regarding the move from a vendor-specific edition to a GA edition. Attached are some screenshots from the upgrade.
Congrats!!
you really did a great job. not everyone can easily upgrade from other version to the latest. sometimes, you really need someones help in order to overcome a failure. Congrats.