I just upgraded to ESXi 5, however there was no support for the JMicron ATA Controller on my EP45-UD3L board.
Vib can be installed into a running instance like so:
#set acceptance to community support if not already selected esxcli software acceptance set --level=CommunitySupported esxcli software vib install -v http://dustint.com/code/pata-jmicron-0.1.5.x86_64.vib
Note that I could not get the package to work with an existing instance and had to do a “fresh” install of ESXi (rather than installing the package or an in-place upgrade).
Source is on GitHub: https://github.com/51systems/pata_jmicron (with build instructions)